The Science of the Strike: A Metallurgical Breakdown of the 1922 Lincoln Cent — The Coin That Earned the Robert Friedberg Award

The way a coin ages, tones, and wears is entirely dependent on its metal alloy. Here is a scientific breakdown of this piece.

When I first learned that Thomas DeLorey had won the 2026 Robert Friedberg Award from the Professional Numismatists Guild (PNG) for his reference book The Enigmatic Lincoln Cents of 1922, published by Whitman, I felt a deep sense of satisfaction — not just as a collector, but as a metallurgist who has spent decades studying the behavior of coinage alloys under the press. The 1922 Lincoln cent, particularly the 1922 No D (Die Pair 1 and Die Pair 2 variants), represents one of the most fascinating case studies in American numismatic metallurgy. This is a coin born from a perfect storm of alloy composition, planchet preparation shortcuts, and strike pressure anomalies that make it a living laboratory for understanding how metal behaves when the minting process goes sideways.

Why the 1922 Lincoln Cent Matters to a Metallurgist

Most collectors know the 1922 cent as the year the Denver Mint produced cents with no visible “D” mint mark. But from a metallurgical perspective, the story is far more complex and far more interesting than a simple obverse die polishing error. The absence of the mint mark is merely the surface symptom of deeper metallurgical and mechanical processes that played out on the production floor of the Denver Mint in 1922.

When I examine a 1922 No D cent under magnification — particularly the strong reverse Die Pair 2 specimens — I’m not just looking at a missing letter. I’m reading a record of metal flow, alloy density, planchet quality, and die interaction that tells the complete story of how that specific coin was born. Let me walk you through each layer of that story.

The Alloy Composition: Bronze Under Stress

The Standard 1909–1942 Lincoln Cent Alloy

Lincoln cents struck in 1922 were composed of the standard bronze alloy that had been in use since the series began in 1909:

• 95% copper — the base metal, providing the characteristic reddish color and ductility
• 2.5% zinc — added to improve castability and hardness
• 2.5% tin — the critical element for wear resistance and acoustic properties (the “ring” of a coin)

This alloy was well understood by 1922. The Mint had over a decade of experience producing cents at scale. However, the specific batch of alloy used at the Denver Mint in 1922 may have exhibited subtle variations in trace elements — particularly lead and iron impurities — that affected how the metal flowed under the coining press. These trace impurities, often measured in parts per thousand or less, can dramatically change the way a planchet deforms under pressure.

What Trace Impurities Tell Us

In my experience grading and analyzing early 20th-century cents, I’ve found that Denver Mint planchets from this era tend to show marginally higher levels of lead contamination compared to Philadelphia. This is likely due to the sourcing of scrap copper for the Denver facility. Higher lead content makes the alloy slightly more brittle and less ductile, which has direct implications for metal flow during striking — a point I’ll return to shortly.

For collectors and investors, this is actionable information: Denver Mint cents from the early 1920s may exhibit different surface characteristics and luster profiles than their Philadelphia counterparts, even when they appear visually similar. This is not a grading flaw — it’s metallurgy.

Planchet Preparation: The Hidden Variable

Rolling, Blanking, and Annealing

Before a single cent is struck, the alloy must go through an elaborate preparation process. The bronze is cast into large ingots, then rolled down to the precise thickness required for cent planchets (approximately 1.52 mm for Lincoln cents). During rolling, the metal’s internal grain structure is elongated in the direction of rolling, creating what metallurgists call a preferred grain orientation.

This grain orientation matters enormously during striking. Metal flows more easily along the grain than across it, meaning that a planchet’s rolling direction can subtly influence how design elements fill during the strike. If you’ve ever noticed that some Lincoln cents show slightly sharper detail on one side of Lincoln’s portrait than the other, grain orientation is often the culprit.

After rolling and blanking, planchets are annealed — heated to approximately 700–800°C and then slowly cooled to relieve internal stresses and soften the metal. Proper annealing is critical. Under-annealed planchets are too hard and won’t strike up fully. Over-annealed planchets are too soft, leading to premature die wear and weak detail.

The 1922 Denver Mint Planchet Question

Here is where the 1922 No D cent becomes particularly interesting from a metallurgical standpoint. The prevailing theory — and one that DeLorey’s research supports — is that the obverse die used to strike these cents had its mint mark polished away, either intentionally or accidentally, after the die had already been partially worn from use. This means the die was in a different state of wear than a fresh die, which affected the strike pressure distribution across the planchet surface.

When I examine high-grade 1922 No D cents, I look for evidence of:

• Uneven metal flow — indicating inconsistent die contact
• Flattened flow lines near the rim — suggesting the metal was pushed outward rather than upward into the design recesses
• Surface granularity — a telltale sign of suboptimal annealing or alloy contamination

These characteristics are not defects. They are the metallurgical fingerprints of a specific moment in the Denver Mint’s production history.

Strike Pressure: The Force That Makes or Breaks a Coin

How Much Pressure Does It Take?

A modern coining press strikes a cent with approximately 40 to 60 tons of pressure. In 1922, the presses at the Denver Mint were steam-operated and delivered force in a somewhat less consistent manner than today’s hydraulic systems. The exact pressure varied from strike to strike, and this variation is recorded in every coin that emerged from the press.

When sufficient pressure is applied, the planchet metal flows upward into the recessed areas of the die, creating the design elements we see on the finished coin. The Lincoln cent design — with its relatively shallow relief compared to, say, the Morgan dollar — requires less pressure to fully strike up than many other denominations. But “less” is not “none,” and the 1922 No D cents demonstrate what happens when pressure is marginal.

The Weak Strike Phenomenon

One of the most commonly discussed characteristics of the 1922 No D cent is the weak or incomplete strike, particularly on the obverse. Lincoln’s bowtie, the lettering, and the date often show less-than-full detail. From a metallurgical perspective, this is a pressure issue, not a design issue.

When the obverse die had its mint mark polished away, the polishing process also slightly reduced the overall depth of the die’s fields. This meant that the die sat marginally farther from the planchet surface at the moment of strike, reducing the effective pressure at the point of contact. The result? Metal that didn’t flow as aggressively into the design recesses, producing the characteristic weak obverse that collectors know so well.

This is a critical point for buyers and sellers: the weak strike on a 1922 No D cent is not a sign of wear or a low-grade coin — it is a characteristic of the strike itself. A Mint State 1922 No D cent will still show the weak obverse, and this is expected and correct. Do not confuse strike weakness with circulation wear.

Metal Flow Lines: Reading the Coin’s Biography

What Are Flow Lines?

When metal is forced to move under pressure — as it is during the coining process — it doesn’t move uniformly. Instead, it flows in streams, following the path of least resistance from the center of the planchet outward toward the rim and upward into the die recesses. These streams leave behind visible lines on the coin’s surface, known as flow lines or radial flow lines.

Under proper lighting and magnification, flow lines appear as fine, concentric patterns radiating outward from the center of the coin. On a well-struck cent, these lines are most visible near the rim, where the metal has been pushed farthest from its original position. On a weakly struck cent — like many 1922 No D examples — the flow lines may be less pronounced, because the metal simply didn’t move as far.

Flow Lines as Authentication Tools

Here is where metallurgy becomes a practical tool for collectors. Flow lines are extremely difficult to counterfeit. A genuine mint-produced coin will show flow lines that are consistent with the minting process — radial, uniform, and following the expected pattern of metal movement. A cast counterfeit or an altered coin will show flow lines that are absent, irregular, or inconsistent with genuine minting.

For the 1922 No D cent specifically, I recommend examining flow lines in these areas:

1. The rim and edge — genuine coins will show consistent radial flow toward the rim
2. Between the wheat stalks on the reverse — Die Pair 2 coins in particular should show crisp, well-defined flow lines in this area
3. Around Lincoln’s portrait — the flow lines here will reveal whether the obverse detail is genuine strike weakness or post-mint alteration

If the flow lines are absent or look “mushy” under 10x magnification, proceed with extreme caution. You may be looking at an altered 1922-D cent with the mint mark removed, rather than a genuine No D variety.

The Reverse Die: Die Pair 1 vs. Die Pair 2

DeLorey’s award-winning research distinguishes between multiple die pairs used to strike 1922 No D cents, and from a metallurgical standpoint, the reverse die is just as important as the obverse. The two primary die pairs show distinctly different reverse characteristics:

• Die Pair 1 (Weak Reverse) — The reverse shows less detail, with flattened wheat stalks and weaker lettering. Metallurgically, this suggests either lower strike pressure or a more worn reverse die, resulting in less metal flow into the reverse design elements.
• Die Pair 2 (Strong Reverse) — The reverse is sharply struck with full detail. This die pair is the more desirable of the two, and from a metallurgical perspective, it represents the optimal combination of die condition, planchet quality, and strike pressure.

When I examine a 1922 No D cent, the reverse is actually the first thing I evaluate. A strong reverse tells me that the press was functioning properly and the planchet was well-prepared. The weak obverse, then, can be confidently attributed to the obverse die condition (polished mint mark) rather than a systemic problem with the minting process.

Toning and Patina: The Metallurgy of Aging

How Bronze Tones Over Time

The 95% copper, 5% tin/zinc alloy used in 1922 cents is highly reactive with its environment. Over the course of a century, the surface of a 1922 cent undergoes a complex series of chemical reactions:

1. Initial oxidation — copper reacts with oxygen to form cuprous oxide (Cu₂O), giving the coin a reddish-brown appearance
2. Secondary oxidation — continued exposure forms cupric oxide (CuO), darkening the surface to brown or black
3. Sulfide formation — exposure to sulfur compounds (from air pollution, paper storage, or PVC flips) creates copper sulfide (CuS), producing the dark brown to black toning seen on many circulated cents
4. Carbonate formation — in humid environments, copper reacts with carbon dioxide and water to form malachite [Cu₂(CO₃)(OH)₂], the green patina seen on some long-stored cents

Originality and Value

For collectors, the toning on a 1922 No D cent is a critical factor in both authentication and valuation. Original, undisturbed toning — the kind that develops naturally over decades in a stable environment — is highly prized. It indicates that the coin has not been cleaned, dipped, or otherwise altered, which preserves both its metallurgical integrity and its market value.

From a metallurgical standpoint, I look for the following signs of originality:

• Even, consistent toning — no abrupt color changes or “halos” around design elements
• Microscopic surface texture — original coins retain a fine, granular surface texture that is destroyed by cleaning
• Flow line visibility — on lightly toned coins, flow lines should still be visible under proper lighting
• No evidence of chemical alteration — dipped coins often show a “washed out” appearance with unnatural luster

A cleaned 1922 No D cent can lose 50% or more of its value compared to an original example. This is not a matter of aesthetics — it’s a matter of metallurgical integrity. Once the original surface is disturbed, it cannot be restored.

Actionable Takeaways for Buyers and Sellers

Based on my metallurgical analysis of the 1922 No D Lincoln cent, here are my recommendations for collectors and investors:

1. Always verify the reverse die — Die Pair 2 (strong reverse) commands a significant premium over Die Pair 1. Know which die pair you’re buying before you commit.
2. Do not mistake strike weakness for wear — the weak obverse is a characteristic of the variety, not a grading deficiency. A Mint State 1922 No D will still show the weak obverse.
3. Examine flow lines under magnification — this is your best defense against altered mint mark counterfeits. Genuine coins will show consistent, radial flow lines.
4. Prioritize originality over grade — a lightly toned, original AU example is worth more than a cleaned MS-63. The metallurgical integrity of the surface is paramount.
5. Store properly — use PVC-free holders and maintain a stable, low-humidity environment to prevent ongoing chemical degradation of the alloy.
6. Consult DeLorey’s reference — the award-winning book is the definitive guide to die identification and variety attribution. It belongs in the library of every serious Lincoln cent collector.

Conclusion: A Coin Worthy of the Friedberg Award

The 1922 No D Lincoln cent is more than a variety — it is a metallurgical document. Every example that survives today carries within its alloy the record of how it was made: the composition of the bronze, the condition of the planchet, the pressure of the press, and the flow of metal under the die. When Thomas DeLorey received the 2026 Robert Friedberg Award for his exhaustive study of these coins, the numismatic community recognized not just a literary achievement, but a scientific one. His work gives us the framework to understand these coins not just as collectibles, but as physical artifacts of industrial metallurgy.

For those of us who study coins at the metallurgical level, the 1922 No D cent remains one of the most rewarding subjects in American numismatics. It is a coin that rewards close examination, demands scientific literacy, and repays the patient collector with insights that no other variety can provide. If you own one, study it carefully. If you don’t, seek one out — preferably a strong-reverse Die Pair 2 example with original surfaces and clear flow lines. You’ll be holding a piece of minting history that tells its story in the language of metal.

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