I learned of a product this week that is used by my sculptor friends which could have a delirious effect in numismatics. It is a polymer that can enlarge or reduce a relief item, as a coin or medal. A sculptor wrote about this product in the latest issue of AMSA Members Exchange. She used it in her modelling of small reliefs and sculpture-in-the round.

She also stated it could be used for resizing medals. That was the red flag in my face. Widespread use of this polymer could alter genuine numismatic items by changing their size. I foresee some eBay seller offering one of these as a "one-of-a-kind pattern."

The polymer -- I refuse to name the product to discourage copyists -- is fairly easy to use. It is mixed with very cold water and the genuine item is pressed into the rubbery substance to form a mold. It requires time to cure, enlarging as it dries.

A similar polymer product reduces the size. "I have reduced a 15-inch model down to a 3-inch medal in four steps, repeating this process," she boasts.

A positive cast must be made from this mold -- or two different molds for a two-sided medal. Perhaps the end product would not fool an experienced numismatist, provided the original was a struck medal.

What if the genuine were a cast medal, as so many productions are of such form -- medallic objects made by modern medallists the world over, Or worse yet, Renaissance medals of tremendous rarity and value, most all of which are cast. For readers who would like to learn the diagnostics between striking and casting, read my article at my MEDALBLOG: How to Tell Struck Medals from Cast(medalblog.wordpress.com/2012/03/26/how-to-tell-struck-medals-from-cast/).

Numismatists easily recognize oversize flans of past attempts to make oversize copies. This was accomplished by placing the coin between two hard-rubber slabs. This ensemble is then placed in a vise and squeezed. It might take several attempts to make a significant enlarged item.

Experienced numismatists know there is no such thing as a '"rubber die'" that can strike oversize or undersize items. For small size coins these are often removed from aluminum encased frames.

Thus there are no oversize or undersize item made at the mint. These are most often homemade fabrications.