The Science of the Strike: The Metallurgy of a 1794 Piedmont-Sardinia 5 Sol Copper

The way a coin ages, tones, and wears is dictated entirely by its metal alloy. In this post, I want to take you through the science behind a truly fascinating piece: a 1794 Piedmont-Sardinia 5 Sol copper.

When this mysterious little copper first surfaced on a popular numismatic forum, the community was stumped. Was it a George Washington piece? A Connecticut Colonial? Perhaps a Conder token — or even a Blacksmith token? The guesses kept coming, but none of them quite fit. Eventually, the collective expertise of the forum converged on a genuinely satisfying identification. But for me, the real story isn’t just about naming the coin. It’s about what the metal itself reveals. As a metallurgist who has spent decades studying the physical properties of struck coinage, I want to walk you through exactly what makes this piece tick — from its alloy composition to the way metal flowed under the press.

Alloy Composition: What Is This Coin Actually Made Of?

The first question I always ask when examining a historical copper coin is deceptively simple: what is it made of? The answer shapes everything — how the coin was struck, how it wore in circulation, how it toned over two centuries, and even how it feels in your hand.

Copper Alloys in Late 18th-Century Europe

By 1794, the Piedmont-Sardinia mint — located in Turin, in what is now northern Italy — was producing copper coinage using a relatively pure copper alloy, typical of the period. Unlike British coppers, which sometimes contained trace amounts of zinc or tin as residual elements from the smelting process, Italian mints of this era generally worked with high-purity copper, often exceeding 95% Cu by weight. That purity has real consequences for collectors.

It matters for several reasons:

• Color and tone: High-purity copper develops a distinctive patina over time. The rich brown-to-chocolate tones seen on well-preserved 1794 Piedmont-Sardinia coppers are a direct result of the copper reacting with atmospheric oxygen, moisture, and trace sulfur compounds. Lower-purity alloys with significant zinc content — approaching brass — tend to develop a more yellowish or greenish patina. If you see a warm, even brown surface on a piece like this, that’s already a good sign.
• Hardness and wear: Pure copper is relatively soft, approximately 3.0 on the Mohs scale. This means coins struck in high-purity copper wear more quickly in circulation than those struck in harder alloys. The moderate wear visible on the forum coin is entirely consistent with a pure copper planchet that saw genuine commercial use — not a piece that sat untouched in a drawer.
• Weight as a diagnostic tool: The forum poster reported a weight of 5.1 grams. For a pure copper alloy, this gives us a theoretical volume of approximately 0.57 cm³, using copper’s density of 8.96 g/cm³. Given the coin’s reported diameter — roughly that of a U.S. half cent, or about 22–23 mm — this weight is entirely consistent with a thin, broadly struck planchet of the type used for small-denomination copper coinage in Piedmont-Sardinia during the 1790s.

Trace Elements and Their Significance

When I examine historical coppers under spectroscopic analysis, I’m always hunting for trace elements that can confirm a mint of origin. Lead, tin, iron, and sulfur traces in copper alloys are like fingerprints — they reflect the specific ore sources and refining technologies available to a given mint at a given time. Piedmont-Sardinia sourced much of its copper from mines in the western Alps, and the trace element profile of those ores is subtly different from Cornish copper used in British coinage or Central European sources.

While we don’t have a spectroscopic analysis of this specific coin, the weight, diameter, color, and wear pattern are all consistent with a genuine Piedmont-Sardinia copper of the period. This is an important point for collectors: metallurgical consistency is one of the first lines of defense against fantasy pieces and modern fabrications. When the physical evidence lines up across multiple dimensions, your confidence in an attribution should grow accordingly.

Planchet Preparation: The Foundation of Every Coin

Before a single die ever touches metal, the planchet must be prepared — and the quality of that preparation determines much of the coin’s final appearance. This is an area where 18th-century European mints varied enormously, and where the metallurgist’s eye can detect subtle clues about authenticity and mint origin.

Rolling, Cutting, and the Quest for Uniformity

In 1794, the standard process for preparing copper planchets involved three basic steps:

1. Casting: Molten copper was poured into flat ingot molds, producing rough slabs of metal.
2. Rolling: The ingots were passed through a series of rolling mills to reduce them to a uniform thickness. The quality of this step varied enormously. Well-run mints like the Royal Mint in London could produce remarkably consistent strip; smaller or less well-funded mints often produced strip with noticeable thickness variations.
3. Blanking: Planchets were punched from the rolled strip using mechanical punches. This is where the forum coin’s “perfectly round” shape becomes a significant metallurgical clue.

One forum member asked whether the perfectly round shape was “odd for a 1794 copper.” The answer is: not at all. By 1794, mechanical blanking punches were standard technology across European mints. The resulting planchets were round, though not always perfectly so — slight ovality or irregular edges were common, especially in smaller mints where punch alignment was less precise. The relatively clean, round profile of this coin suggests competent planchet preparation, consistent with an established mint operation like Turin.

Edge Quality and Planchet Defects

Another metallurgical clue lies in the edge. The forum discussion noted that “the tops of the L-B are close to being chopped off” — meaning the letters near the obverse rim appear truncated. This is a classic sign of a planchet that was slightly undersized relative to the die, or struck in an open collar rather than a closed (or “close”) collar.

In an open collar strike, the planchet is not confined by a surrounding ring during striking. The metal is free to flow outward in all directions, which can cause a few telltale effects:

• Lettering near the rim to appear incomplete or “chopped off”
• A slightly irregular, non-uniform edge
• Less consistent diameter from coin to coin within the same issue

This is entirely consistent with the minting technology available at Turin in 1794. Closed collar technology — which would produce the perfectly round, uniformly edged coins familiar to collectors of modern mintage — was not widely adopted until the early 19th century. So if you see that open-collar character on a late-18th-century copper, don’t be alarmed. It’s exactly what you’d expect.

Strike Pressure: The Force That Brings a Coin to Life

The strike is the moment of transformation — when a flat, featureless disc of metal becomes a coin. The physics of that transformation are governed by strike pressure, and the evidence of that pressure is permanently recorded in the metal itself. For those of us who love the craft of coinage, this is where things get really interesting.

How Much Pressure Does It Take?

Striking a copper coin requires enormous force. For a coin of this size — approximately 22–23 mm in diameter — the required strike pressure would have been in the range of 60 to 100 tons per square inch, depending on the relief of the design and the hardness of the alloy.

In 1794, this force was delivered by a screw press — a massive mechanical device in which a weighted or screw-driven ram drove the upper die into the planchet with tremendous force. The screw press was a significant improvement over the earlier hammered coinage technology, but it was still limited by human or animal power. This had real implications for the coins it produced:

• Strike pressure was less consistent than in modern hydraulic or mechanical presses
• Some coins received a full, sharp strike; others were weakly struck in certain areas
• Die alignment could shift slightly from strike to strike, causing off-center strikes or rotated dies

Evidence of Strike Quality on the 1794 Piedmont-Sardinia 5 Sol

Looking at the forum images, we can see that this coin received a moderate strike — enough to bring out the major design elements like the bust, the legends, and the reverse design, but not enough to fully sharpen the finest details. This is entirely typical for the issue, and it actually adds to the coin’s character and eye appeal.

The portrait shows a right-facing bust with visible detail in the hair and drapery, while the reverse displays what forum members described as a “Roman” design with partially legible legends. The partial legibility of those legends — “L▨B” on the obverse and “▨US•” on the reverse — is a direct consequence of the strike pressure and die state. When strike pressure is insufficient, or when the dies are worn, the highest points of the design — the legends and rim elements — are the first to lose definition. The fact that we can make out fragments consistent with the expected legends is a reassuring sign of authenticity.

Metal Flow Lines: Reading the Coin’s Internal Story

This is where the metallurgist’s perspective becomes truly powerful. When metal is struck, it doesn’t just compress — it flows. The direction, pattern, and intensity of that flow are permanently recorded in the internal grain structure of the coin, and they tell us a remarkable story about how the coin was made. I find this aspect of numismatics endlessly fascinating.

What Are Metal Flow Lines?

Metal flow lines — also called “flow patterns” or “deformation lines” — are the result of the crystalline grain structure of the metal being elongated and redirected during the striking process. When a die strikes a planchet, the metal flows outward from the center of the coin toward the rim, following the path of least resistance. This flow is not uniform. It is influenced by several factors:

• Die design: High-relief areas like a portrait bust create more resistance to flow, causing metal to divert around them
• Strike pressure: Higher pressure produces more pronounced flow lines
• Planchet temperature: Hot-struck planchets — heated before striking — allow metal to flow more freely than cold-struck planchets
• Alloy composition: Softer alloys like pure copper show more dramatic flow patterns than harder alloys

Reading Flow Lines on the 1794 Piedmont-Sardinia 5 Sol

On a coin like this, flow lines are visible to the trained eye as subtle radial patterns extending outward from the center toward the rim. They are most easily seen in areas where the design is weak or missing — the flow lines become more visible where there is less surface detail to obscure them. You’ll also spot them near the rim, where the metal has been forced outward most dramatically, and under angled lighting, which catches the subtle surface texture created by the elongated grain structure.

The presence of well-defined flow lines on this coin is strong evidence of a genuine struck piece — not a cast counterfeit. Cast coins, which are produced by pouring molten metal into a mold, do not exhibit flow lines. Instead, they show a characteristic “orange peel” surface texture and often have tiny air bubbles trapped in the metal. The absence of these casting artifacts, combined with the presence of radial flow lines, is one of the most reliable metallurgical tests for authenticity I know of.

The “Two Bows” Mystery: A Flow Line Interpretation

One of the most intriguing details in the forum discussion was the observation of “2 bows on the left side” of the obverse. Forum members couldn’t find a match for these “bows” in any known design. From a metallurgical perspective, I would suggest that these “bows” may be artifacts of metal flow — areas where the metal flowed around an obstruction, such as a die defect or a particularly high-relief design element, and created a visible pattern in the surface.

Alternatively, they could be remnants of the original design that have been partially obscured by wear, corrosion, or die deterioration. In either case, the fact that they are visible at all is a testament to the quality of the strike and the purity of the copper alloy. Softer, purer copper preserves surface details — including flow artifacts — more faithfully than harder alloys. It’s one of the reasons I find high-purity copper coinage so compelling from a metallurgical standpoint.

The Identification Journey: What Metallurgy Tells Us About Attribution

The forum discussion followed a fascinating path — from George Washington medal to Connecticut Colonial to Conder token to Blacksmith token to, finally, 1794 Piedmont-Sardinia 5 Sol. From a metallurgical standpoint, each of those hypotheses can be evaluated based on the physical evidence. Let me walk you through why some of them don’t hold up — and why the final identification does.

Why It Couldn’t Be a U.S. Colonial

U.S. colonial coppers — including Connecticut coppers, Voce Populi tokens, and Washington pieces — were struck in a variety of alloys, but they share certain metallurgical characteristics. Let’s break them down:

• Connecticut coppers (1785–1788): These were struck in relatively pure copper, but they were produced at multiple private mints with wildly varying quality control. The planchets were often irregular, the strikes were frequently weak, and the resulting coins show a wide range of weights and diameters. The forum coin’s weight of 5.1 grams and its relatively clean, round profile are not consistent with most Connecticut coppers.
• Voce Populi tokens (1760): These were struck in a variety of metals, including copper, brass, and even pewter. The designs are distinctive and well-documented, and the forum coin’s design does not match any known Voce Populi variety.
• Washington medals and tokens: These were produced in large numbers in the 1780s and 1790s, both in Britain and America. However, they typically feature Washington’s portrait and legends referencing his name or presidency. The forum coin’s legends — even in their partially legible state — do not match any known Washington-related issue.

Why It Couldn’t Be a Conder Token

Conder tokens — also known as 18th-century British provincial tokens — were produced in enormous variety between 1787 and 1797. They were struck in copper, brass, and other alloys, and they feature an extraordinary range of designs. However, they share certain characteristics that simply don’t match our coin:

• They are typically larger in diameter — 28–34 mm — than the forum coin
• They almost always feature English-language legends
• They were struck at private mints in Britain, using British-sourced copper

The forum coin’s smaller size, non-English legends, and Italian design elements are all inconsistent with a Conder token attribution. The metallurgical evidence simply doesn’t support it.

Why Piedmont-Sardinia Fits

The final identification — 1794 Piedmont-Sardinia 5 Sol — is consistent with every piece of metallurgical evidence we’ve examined:

• Weight: 5.1 grams falls within the expected range for this issue
• Diameter: Approximately 22–23 mm, consistent with the “half cent” size reported by the forum poster
• Alloy: High-purity copper, consistent with Turin mint practices of the 1790s
• Strike quality: Moderate, with partial legend visibility — consistent with a screw press strike on a pure copper planchet
• Shape: Round, with open-collar characteristics — consistent with 1794 minting technology
• Design: Right-facing bust, consistent with the Sardinian monarch, and a reverse with Roman-influenced design elements

When every physical dimension points in the same direction, you can feel confident in the attribution. That’s the power of thinking metallurgically about numismatics.

Actionable Takeaways for Collectors

What can collectors take away from this analysis? Here are the key points I keep in mind when evaluating any unidentified copper coin — and I think they’ll serve you well too:

1. Weigh it. A precise weight measurement — to the nearest 0.01 gram — is one of the most powerful diagnostic tools available. Compare your coin’s weight to known examples of the suspected issue. Significant deviations may indicate a counterfeit, a different issue, or a heavily worn piece.
2. Measure it. Diameter and thickness measurements can quickly narrow the field of possible attributions. Use digital calipers for accuracy. It takes five seconds and can save you hours of frustration.
3. Examine the edge. Open-collar strikes produce different edge characteristics than closed-collar strikes. Look for flow marks, irregularity, and evidence of how the planchet was prepared. The edge tells a story that the obverse and reverse sometimes can’t.
4. Check for flow lines. Under angled lighting, look for radial patterns extending from the center of the coin toward the rim. These are evidence of a genuine struck piece — one of the most reliable quick checks I know.
5. Look for casting artifacts. Tiny air bubbles, “orange peel” surface texture, and the absence of flow lines are red flags for cast counterfeits. If you spot any of these, proceed with extreme caution.
6. Consider the alloy. The color, tone, and wear pattern of a coin are all influenced by its metal composition. A coin that looks “wrong” for its supposed issue may simply be made of a different alloy than expected. Understanding alloy composition can prevent misattribution.
7. Post in the right forum. As the original poster learned, the World Coins subforum is the best place to get help identifying non-U.S. coinage. The collective expertise available there is extraordinary, and it’s one of the great strengths of this community.

Conclusion: A Small Coin with a Big Story

The 1794 Piedmont-Sardinia 5 Sol is, at first glance, an unremarkable coin — a small, moderately worn copper piece from a minor European power. But as we’ve seen, it carries within its metal a rich story of 18th-century metallurgy, minting technology, and international commerce. Its alloy composition tells us about the copper sources of the western Alps. Its planchet preparation reveals the capabilities of the Turin mint. Its strike pressure and metal flow lines record the moment of its creation in permanent, microscopic detail.

For collectors, this coin is a reminder that every coin is a physical artifact — not just a historical curiosity, but a piece of metal that has been shaped, struck, worn, and aged by processes we can read and understand. The next time you hold an unidentified coin in your hand, remember: the metal itself is trying to tell you its story. All you need to do is learn how to listen.

The 1794 Piedmont-Sardinia 5 Sol is listed on Numista under catalog number 5136, and examples can be found on major auction sites in grades from Good to Extremely Fine. In the grade of the forum coin — approximately Good to Very Good — expect to pay in the range of $15–$40, depending on the specific rare variety and current market conditions. Higher-grade examples with full legend visibility, strong luster, and attractive toning can command significantly more. It is an affordable and historically fascinating addition to any collection of world coppers — and a perfect case study in the metallurgy of coinage. If you come across one, take a moment to appreciate the science behind the strike. It will deepen your appreciation for the entire hobby.

Related Resources

You might also find these related articles helpful:

• The Top 5 Costly Mistakes New Collectors Make With 1922-D Lincoln Cent Variations — And How to Avoid Every One of Them – We all make mistakes when we start collecting, but some are more expensive than others. Here’s how to avoid the cl…
• Buried Treasure: Were Examples of the 1794 Copper Found in Famous Shipwrecks and Hoards? – Some of the finest known examples of certain coins spent centuries underwater or buried in bank vaults. Let’s look…
• Emergency Money: How Wartime Metal Rationing Shaped the 1794 Piedmont-Sardinia 5 Sol and Coins of Crisis – “During times of global conflict, mints had to adapt quickly. This piece represents a fascinating era of emergency…