How Romans Tested Fake Coins

Marcus Valerius

Step into the Argiletum with me for a second. It is mid morning, the year 110 under Emperor Trajan, and the noise in this street... well, it is enough to deafen a mule. You have shoemakers shouting, pie sellers hawking hot sausages, and thousands of boots shuffling over the basalt paving stones. I just handed over a jar of my red Sabine wine to a customer. He handed me a silver denarius. Standard trade, right? But before I slip that coin into my tunic pouch, I do what every single person in Rome does without even thinking. I let it drop. I toss it down onto a flat basalt stone at my feet. A good, solid silver coin, a real denarius, hits the stone and sings. It gives you a high, clear, musical chime that hangs in the air like a tiny bell. But this one? Thud. A dead, heavy, leaden clack. My heart drops right into my leather sandals.

Marcus Valerius

You see, I have just been handed what we Romans call a subaeratus. That is our official Latin word for it, literally meaning copper below. You might also hear folks call it a fourree. It looks like solid silver on the surface. It carries the sharp, proud profile of Emperor Trajan, bold nose, laurel wreath, fine lettering and all. But beneath that paper thin skin of silver? Pure, cheap red copper. And the trade of making these fake coins, it is practically a dark art in the alleyways behind the Subura. The fakers take a blank core of copper, a flan, and wrap it tightly in thin silver foil. Then, to make sure the silver skin does not just peel off the moment it leaves their fingers, they sprinkle a powdered mixture of copper and silver right between the layers. When they heat that wrapped sandwich and hit it hard with a heavy iron die and hammer, that powdered blend melts at a lower temperature than either metal alone. It creates what the craftsmen call a eutectic bond, fusing the silver skin tightly to the cheap core. The coin comes out looking brilliant, fresh from the mint.

Marcus Valerius

But you cannot fool a stone, and you cannot fool a trained ear. The Greek philosopher Epictetus actually wrote about this exact thing in his Discourses. He observed how Roman coin assayers drop a denarius again and again, listening intently to its ring, practically acquiring the subtle ear of a musician just to guard against deception. And that is exactly where I am walking right now, taking my dodgy coin down the street to an official street assayer, a nummularius. He sits right on the edge of the Forum behind a sturdy wooden table, his mensa, with his scales and testing tools laid out before him. Around us, every tavernkeeper, baker, and fishmonger is habitually flicking every coin they touch against their wooden or stone counters before handing over a single loaf of bread or cup of wine. In Rome, trust is nice, but the sound of metal is truth.

Marcus Valerius

I step up to the table and slide the quiet denarius onto the nummularius's board. He does not even look up at me at first. He just picks it up with thick, ink stained fingers and begins what every street merchant knows as the four stage assay. First, his eyes. He lifts the coin right up to the sunlight, turning the edge to inspect the rim. He is looking for a tiny green bloom, aerugo, where moisture might have seeped between the foil seams and corroded the hidden copper core. Next comes his hearing. He picks up a smooth bronze plate on his table, lifts the coin three inches, and drops it. Clack. That same dull, dead thud. He shakes his head softly.

Marcus Valerius

Then, touch and weight. He lays the coin onto one pan of his delicate brass scales and places an official silver weight on the other. Copper is lighter than silver, so a plated fake usually comes up short unless the counterfeiter made the coin unnaturally thick. Fourth, he reaches for his touchstone, the lapis lydius, a smooth piece of black stone brought all the way from Lydia. He rubs the coin's edge firmly against the black surface, leaving a shiny metallic streak. Then he compares that mark to known samples of pure silver and raw copper. But even after all four tests, the nummularius wants absolute certainty before he renders his final judgment.

Marcus Valerius

He pulls out a small iron chisel and a heavy wooden mallet. He sets the coin flat on his anvil block, aligns the chisel blade right across Emperor Trajan's face, and bring the mallet down with a sharp crack! That is the test cut, the incisio. The iron blade slices straight through the thin silver skin, leaving a deep notch right across the surface. And there, sitting inside the gleaming white cut, is an unmistakable flash of raw, bright red copper. Exposed. Caught red handed.

Marcus Valerius

Now, you might assume that this is the moment where the guards step in, grab the fake coin, melt it down, or arrest me for holding it. But this is Rome, my friend. Our laws with money are far more practical than that. The nummularius does not confiscate the coin. He simply hands the notched, ruined coin back to me across his wooden table. Because even though it is an exposed fourree, that coin still contains a tiny skin of silver and a solid bit of copper. So what happens to it? I walk right down into the crowded tenement lanes of the Subura, where poor street vendors and market stalls will still take a notched coin. They will not take it at its full face value of one denarius, of course. But they will accept it at a discount, say three quarters or half price, based purely on the scrap value of its metal. So the notched fake keeps right on circulating through the city, passing from hand to hand, scarred but still spending.

Marcus Valerius

I tuck my notched denarius into my tunic pocket and turn back toward my wine shop. It is just another morning in the capital of the world. A place where emperors build grand marble monuments, but ordinary citizens survive on keen eyes, sharp chisel cuts, and a sharp ear for metal. Remember that next time you hear a coin rattle on a counter. In Trajan's Rome, you never trust the imperial stamp until you have heard the ring of the stone. Take care out there.