How to Spot Rare Errors on Denver Mint Coins: A Variety & Error Hunter’s Guide to Die Cracks, Double Dies, and Mint Mark Variations

Most people look right past the tiny details that can turn a common coin into a rarity worth thousands. I’ve been hunting error coins and die varieties for over two decades now, and I can tell you from hard-won experience — the difference between a coin worth face value and one worth a car payment often comes down to a millimeter of displaced metal, a hairline crack in a die, or a mint mark that was punched in twice. If you’re not training your eye to catch these details, you’re leaving serious money on the table.

I recently had the privilege of attending the Denver Coin Expo — one of the premier shows in the Rocky Mountain region with over 130 dealers — and I want to share some of the most important lessons I’ve learned over the years about identifying the errors and varieties that matter. Whether you’re scouring dealer tables, picking through OBW rolls (which, as fellow collectors know, bring a special kind of joy), or examining your own collection under magnification, this guide will sharpen your eye and help you spot what others walk right past.

Why Error Coin Hunting Matters More Than Ever

The error coin market has matured dramatically in the last twenty years. What was once a niche corner of numismatics — dismissed by traditional collectors who preferred “problem-free” coins — has become one of the most vibrant and profitable segments of the hobby. Third-party grading services like ANACS (which had a strong presence at the Denver show) now attribute and encapsulate errors alongside their standard grading services. PCGS and NGC have followed suit. This institutional recognition has brought legitimacy and liquidity to the error market that simply didn’t exist a generation ago.

But here’s the thing most newcomers don’t realize: the vast majority of errors are still being found in circulation, in rolls, and in dealer bargain bins. You don’t need to be a deep-pockets collector cornering the market on early silver dollars. You need knowledge, patience, and a good loupe. That’s what this guide is about.

The Four Categories of Errors Every Collector Must Know

Before we dive into specifics, let me lay out the fundamental framework. In my experience grading and attributing coins, errors fall into four broad categories:

1. Planchet Errors — Problems with the blank metal strip or the blank itself before it ever reaches the striking press. These include clipped planchet errors, wrong planchet errors (a dime struck on a cent blank, for example), laminations, and split planchets.
2. Die Errors — Problems with the die used to strike the coin. This is where die cracks, doubled dies, die chips, and cuds fall. These are the errors I want to focus on most in this article because they’re the most commonly overlooked.
3. Strike Errors — Problems that occur during the actual striking process. Off-center strikes, broadstrikes, brockages, and die caps are the most dramatic and visually striking examples.
4. Mint Mark and Die Variety Errors — Subtle differences in mint mark placement, size, or style, as well as repunched mint marks (RPMs) and other die-specific variations that can dramatically affect numismatic value.

Identifying Die Cracks: The Hidden Treasure in Plain Sight

Let’s start with die cracks, because in my opinion, they are the single most underappreciated error category in all of numismatics. A die crack occurs when the hardened steel die that strikes coins develops a fracture from repeated use. Metal flows into that fracture during striking, producing a raised line on the finished coin.

What to Look For

Die cracks can range from nearly invisible hairlines to dramatic, jagged raised lines that traverse an entire coin. Here’s how I approach examining any coin for die cracks:

• Hold the coin at a low angle under a strong light source. Die cracks appear as raised lines on the coin’s surface — they are not incised or engraved. Tilt the coin so the light rakes across the surface, and the raised metal of a die crack will cast a tiny shadow.
• Check high-stress areas first. Die cracks tend to originate at the edges of design elements — around lettering, at the rim, and near the junction of the portrait and the field. On Morgan dollars, for instance, I always examine the hair details above Liberty’s ear and the wheat ears on the reverse first.
• Distinguish die cracks from scratches. This is critical. A die crack will be a raised feature that appears on every coin struck by that die (making it a variety, not just damage on a single coin). A scratch is an incuse mark — a gouge in the surface — and is post-mint damage. Under magnification, a die crack will have a slightly rounded, “flowing” cross-section, while a scratch will appear sharp and V-shaped.
• Look for die chips and cuds. When a piece of the die actually breaks away, the resulting area of the coin will show a raised, rounded blob of metal with no design detail. If this occurs over a design element like a date or mint mark, it’s called a “cud” and can be extremely valuable.

Why Die Cracks Matter for Value

Not all die cracks are created equal. A minor, isolated die crack on a common-date Mercury dime might add only a few dollars to the coin’s value. But a dramatic die crack — especially one that connects major design elements or creates a “terminal die state” example — can multiply a coin’s value many times over. Terminal die state coins, where the die was literally falling apart, are among the most sought-after error varieties in the hobby.

I’ve examined coins where a single dramatic die crack turned a $15 Morgan dollar into a $500+ variety. The key is knowing which die states are documented and recognized by the collecting community. Resources like the CONECA ErrorAttribution Manual and variety tracking websites are essential tools in your arsenal.

Doubled Dies: The Crown Jewels of Error Collecting

If die cracks are the underappreciated workhorses of error collecting, doubled dies are the showstoppers. A doubled die occurs when the hub — the master tool used to impress the design into a working die — misaligns during the hubbing process. This creates a secondary image that is offset from the primary image, and every coin struck by that die will show the doubling.

Doubled Die vs. Machine Doubling: Know the Difference

This is where I see the most confusion among newer collectors, and it’s critical to understand the distinction:

• Doubled Die (Class I-VIII): Created during the die-making process. The doubling is part of the die itself and appears on every coin struck by that die. The doubling is typically rounded, spread apart, and visible in multiple design elements. The legendary 1955 Doubled Die Lincoln Cent is the classic example — the doubling in the date and lettering is dramatic and unmistakable.
• Machine Doubling Damage (MDD): Created during the striking process when the die or coin shifts slightly after the initial strike. This produces a flat, shelf-like doubling that is often confused with a true doubled die. Machine doubling is not collectible and adds no value. The key visual difference: machine doubling produces a flat, “pancake-like” shelf, while true doubled die doubling has rounded, three-dimensional separation.

How to Identify a Genuine Doubled Die

Here’s my step-by-step process when I suspect a doubled die:

1. Start with the date and mint mark. These are the most commonly doubled elements and the easiest to verify against known examples. Use a 5x to 10x loupe minimum.
2. Check the lettering. “LIBERTY” on cents, “E PLURIBUS UNUM” on larger denominations — these are prime locations for doubling. Look for notched serifs (the small lines at the ends of letters) and clear separation between the primary and secondary images.
3. Examine the portrait. On Lincoln cents, check the ear, the bowtie, and the truncation of the bust. On Morgan dollars, examine the eyelid, the cap, and the hair curls.
4. Compare to known varieties. For Lincoln cents, consult the Cherrypickers’ Guide to Rare Die Varieties. For Morgan dollars, the VAM (Van Allen-Mallis) system catalogs thousands of die varieties, many of which include doubled die features. For Peace dollars, the TOP (Topeka) attribution system serves a similar function.
5. Verify with magnification and photography. I always photograph suspected doubled dies at high magnification and compare them side-by-side with confirmed examples. If the doubling matches a known variety, you may have a significant find.

Notable Doubled Die Varieties to Hunt For

Here are some of the most important doubled die varieties that still turn up in collections, dealer inventory, and even circulation:

• 1955 Doubled Die Lincoln Cent — The most famous doubled die in American numismatics. Even low-grade examples command thousands of dollars.
• 1972 Doubled Die Lincoln Cent (Obverse) — Dramatic doubling visible in the date and “LIBERTY.” A key date in the error world.
• 1995 Doubled Die Lincoln Cent (Obverse) — One of the most dramatic modern doubled dies, visible in “LIBERTY” and the date even without magnification.
• 1944-P Doubled Die Reverse Lincoln Cent — A wartime variety that is highly sought after.
• Various Morgan Dollar VAMs — Hundreds of Morgan dollar die varieties involve doubling, particularly in the mint mark, date, and lettering. VAM-4 (1878 8 Tail Feathers) and VAM-39 (1887-O) are just two examples of doubled die varieties that command strong premiums.

Mint Mark Variations: Small Letters, Big Money

Mint mark variations represent one of the most fascinating and profitable areas of variety collecting. The mint mark — that small letter indicating which U.S. Mint facility produced the coin — was hand-punched into working dies until the early 1990s. This manual process created a wealth of variations that collectors prize.

Repunched Mint Marks (RPMs)

When a mint worker punched a mint mark into a die and then punched it again — either to strengthen the impression or to correct a misalignment — the result is a repunched mint mark. Under magnification, you can see the ghost of the original punch overlapping the final one.

Here’s what I look for when hunting RPMs:

• Multiple impressions at slightly different positions. The most common RPMs show the original punch slightly above, below, or to the side of the final position. On Lincoln cents, the mint mark is located below the date on the obverse. On Jefferson nickels, it’s to the right of Monticello on the reverse. Know your mint mark locations!
• Notching or thickening of the mint mark. When two punches overlap, the mint mark may appear thicker, notched, or distorted compared to a single-punch example.
• Direction of repunching. RPMs are described by the direction of the repunch relative to the primary mint mark. A “repunched mint mark north” (RPM-N) means the original punch was above the final position. This directional information is essential for proper attribution.

Mint Mark Size and Style Variations

Beyond repunching, the size and style of mint marks varied significantly over the years, and certain combinations of mint mark style with specific dates are rare and valuable. Some key examples:

• 1944-D/S Lincoln Cent — A repunched mint mark where an “S” was punched over a “D.” A recognized variety that commands a premium.
• 1909-S VDB Lincoln Cent — While not an error per se, the combination of the San Francisco mint mark with Victor David Brenner’s initials on the reverse created one of the most famous key dates in American numismatics. The “S” mint mark and “VDB” initials together on a 1909 cent make it a five- to six-figure coin in higher grades.
• Small Date vs. Large Date varieties — On many series, the size of the date digits (which were also hand-punched) creates collectible varieties. The 1960 Lincoln cent, for example, comes in both Small Date and Large Date varieties, and the 1960-D in Small Date is a significant premium coin.

Strike Errors: The Dramatic Showpieces

While die errors and mint mark varieties require a trained eye and magnification, strike errors are often immediately visible and visually dramatic. These are the coins that make people stop at a dealer’s table and say, “What happened to that one?”

Off-Center Strikes

An off-center strike occurs when the planchet is not properly centered between the obverse and reverse dies at the moment of striking. The result is a coin where the design is shifted toward one edge, leaving a blank, unstruck area on the opposite side.

The value of an off-center strike depends on several factors:

• Degree of off-centering. A 5% off-center strike is common and adds modest premium. A 50% or greater off-center strike — where half the design is missing — is dramatic and highly collectible. The most valuable off-center strikes are those where the date is fully visible despite extreme off-centering.
• Denomination. Larger coins (dollars, half dollars) tend to show off-center strikes more dramatically than smaller denominations.
• Presence of a brockage. If an off-center coin sticks to the die and is struck again, it can create a brockage — a mirror-image impression of the design on the opposite side. Brockages are highly collectible and can be extremely valuable.

At the Denver show, I spotted an off-center Eisenhower dollar that had the crowd buzzing. These are the kinds of coins that remind you why you got into this hobby in the first place.

Broadstrikes

A broadstrike occurs when the collar — the circular piece that holds the planchet in place and creates the coin’s edge — fails to engage. The coin is struck without the collar, causing the metal to spread outward in all directions. The result is a coin that is larger in diameter than normal, with a flat, smooth edge and often weak or missing design details at the periphery.

Broadstrikes are particularly dramatic on reeded-edge coins (quarters, dimes, half dollars, dollars), where the absence of reeding is immediately noticeable. I always check the edge of any unusually large coin — if it’s smooth where it should be reeded, you may have a broadstrike.

Die Caps and Brockages

These are among the most visually spectacular errors in existence. A die cap occurs when a planchet sticks to the die and is struck repeatedly, gradually forming a cap-like shape with the design incuse (sunken) on one side and convex on the other. Brockages occur when a stuck coin impresses its mirror image into a subsequent planchet.

Die caps and brockages on silver dollars can be worth hundreds or even thousands of dollars, depending on the clarity of the impression and the condition of the coin.

Specific Errors to Look For: A Collector’s Checklist

After years of hunting, here’s my personal checklist of the most important and commonly overlooked errors that I examine every coin for. I recommend printing this out and keeping it in your show bag:

Lincoln Cents (1909–Present)

• Doubled die obverse or reverse (check date, “LIBERTY,” “IN GOD WE TRUST”)
• Repunched mint marks (especially on Wheat cents 1909–1958)
• Small Date / Large Date varieties (1960, 1970, 1982)
• Off-center strikes (look for visible date on off-center examples)
• Wrong planchet errors (cents struck on dime planchets, zinc cents struck on copper planchets)
• 1943 copper cent (the famous wartime error — only about 40 are known to exist)
• 1944 steel cent (similar rarity to the 1943 copper)
• 1955 doubled die (the king of Lincoln cent errors)
• 1982 zinc cents — check for both Small Date and Large Date in both copper and zinc compositions
• 1992 Close AM reverse (the “AM” in “AMERICA” is nearly touching — a rare variety worth thousands)
• 2009 Lincoln cents — numerous die varieties exist for the bicentennial series

Jefferson Nickels (1938–Present)

• 1939 Doubled Monticello (reverse doubling visible in “MONTICELLO” and “FIVE CENTS”)
• 1942-P Doubled Die Obverse (wartime silver nickel with dramatic doubling)
• 1943-P 3-over-2 Repunched Date
• 1945-P Doubled Die Reverse
• 1954-S/S Repunched Mint Mark
• 1964 Special Mint Set (SMS) specimens — not technically an error, but a rare and valuable variety
• 2004-P and 2005-P “Peace Medal” and “Ocean in View” varieties
• Off-center strikes and broadstrikes (particularly dramatic on the large nickel format)

Morgan Silver Dollars (1878–1921)

• VAM varieties — consult the comprehensive VAM listing for your date and mint
• 1878 8 Tail Feathers vs. 7 Tail Feathers (the 8TF variety is significantly rarer)
• 1888-O “Hot Lips” doubled die obverse (VAM-4) — dramatic doubling on Liberty’s lips
• 1901-P Doubled Die Reverse (VAM-32)
• Repunched mint marks on all dates — Denver (D), San Francisco (S), New Orleans (O), and Philadelphia (no mint mark) all have documented RPMs
• Off-center strikes (particularly dramatic on the large silver dollar format)
• Misaligned die errors (where the obverse and reverse are rotated relative to each other)

Peace Silver Dollars (1921–1935)

• 1921 High Relief (the first year of issue, struck in high relief — not an error, but a key variety)
• 1922 Doubled Die Obverse varieties
• 1928-P Low Mintage (the key date of the series — only 360,649 minted)
• 1934-S (the most valuable date in the series in mint state)
• Repunched mint marks on all dates

Tools of the Trade: What Every Error Hunter Needs

You can’t find what you can see. Here’s my essential toolkit for error and variety hunting:

• A quality loupe (5x to 10x). I prefer a Hastings triplet loupe for its optical clarity. A 5x loupe is great for initial screening; 10x is essential for confirming doubled dies and RPMs.
• A stereo microscope (10x to 40x). For serious variety attribution, a stereo microscope is indispensable. I use mine for every coin I’m considering for purchase.
• A strong, adjustable light source. LED lights with adjustable brightness and color temperature are ideal. Raking light (light held at a low angle to the coin’s surface) is essential for detecting die cracks and other raised features.
• A good reference library. At minimum, I recommend the Cherrypickers’ Guide to Rare Die Varieties (for Lincoln cents and other copper denominations), the VAM book for Morgan dollars, and the CONECA ErrorAttribution Manual for general error identification.
• A digital camera or smartphone with macro capability. Photographing suspected errors allows you to compare them with known examples online and share them with other collectors for attribution assistance.
• A precision scale. Weighing a coin can quickly identify wrong planchet errors. A cent should weigh 3.11 grams (pre-1982 copper) or 2.50 grams (post-1982 zinc). If it weighs significantly different, you may have a wrong planchet error.

Where to Find Errors: Practical Tips for the Hunt

After years of hunting, here are my best strategies for finding errors and varieties:

• Coin shows. Shows like the Denver Coin Expo are treasure troves. Dealers who specialize in errors and varieties often have cases full of material that hasn’t been thoroughly examined. Don’t be afraid to ask to look at coins under your loupe — most dealers welcome serious collectors.
• Roll hunting. Searching through bank rolls of cents, nickels, and dimes is one of the most cost-effective ways to find errors. Wheat cents, wartime silver nickels, and even modern errors still turn up in circulation. I always order multiple rolls from different banks to increase my chances.
• Dealer bargain bins. Many dealers don’t have the time or expertise to examine every coin for errors. Their “junk” or “miscellaneous” bins can be goldmines for the knowledgeable error hunter.
• Online auctions and forums. eBay, Heritage Auctions, and collector forums are excellent sources for error coins. However, be cautious — machine doubling is frequently misrepresented as doubled die doubling in online listings. Always examine the coin in person or request detailed photographs before purchasing.
• Estate sales and inherited collections. Older collections often contain coins that were acquired before the error market developed. These coins may have been sitting in drawers for decades, never examined for varieties.

The Importance of Proper Attribution and Grading

Finding an error is only half the battle. Proper attribution and grading are essential for realizing the full value of your discovery. Here’s my advice:

• Get major errors professionally graded and attributed. ANACS, PCGS, and NGC all offer error attribution services. A professionally attributed and encapsulated error coin will always sell for more than an unattributed example.
• Document your finds. Photograph every error coin from multiple angles, record the weight and diameter, and note any distinguishing features. This documentation is essential for attribution and for establishing provenance.
• Join a collecting community. Organizations like CONECA (Combined Organizations of Numismatic Error Collectors of America) provide attribution services, educational resources, and a community of knowledgeable collectors who can help you identify and value your finds.
• Be patient with attribution. Some varieties are easy to confirm; others require expert examination. Don’t be discouraged if a coin you think is a doubled die turns out to be machine doubling. The learning process is part of the fun.

Conclusion: The Thrill of the Hunt

The Denver Coin Expo reminded me why I fell in love with this hobby. It’s not just about the coins — though the coins are magnificent. It’s about the community, the conversations, the thrill of discovery. Whether you’re examining a beautiful MS68 Buffalo nickel with creamy luster, marveling at a Judd 69 pattern, or holding a common-looking cent that turns out to be a rare doubled die, every coin has a story to tell.

Error and variety collecting is one of the most rewarding pursuits in all of numismatics. It combines historical knowledge, scientific observation, and the pure excitement of the hunt. The errors are out there — in rolls, in dealer cases, in old collections, and in the pockets of people who have no idea what they’re carrying. The only question is whether you’ll have the knowledge and the trained eye to spot them.

So the next time you pick up a coin, don’t just look at the date and mint mark. Look closer. Examine the lettering. Check the edges. Tilt it under the light and look for die cracks. Pull out your loupe and check for doubling. You might just find that the most valuable coin in the room is the one everyone else walked right past.

Happy hunting, and I’ll see you at the next show.

Related Resources

You might also find these related articles helpful:

• How to Properly Insure and Appraise Your Rare Coin Collection: A Fine Art and Collectibles Insurer’s Guide to Protecting Numismatic Investments – A standard homeowner’s policy won’t cover the full numismatic value of a rare collection. Here is how to pro…
• Verdigris and PVC: Saving the 1776-2026 Semiquincentennial Pennies from Environmental Damage – Improper storage is the single greatest threat to any collection. As someone who has spent over twenty years preserving …
• CAC Sticker Impact on Mercury Dimes: How Green and Gold Beans Transform Value, Liquidity, and Collectibility in Today’s Market – In today’s market, a green or gold bean can drastically change a coin’s liquidity and price. Let’s ana…