Know your sprue from your flash?

Over the years, I've written several times about deceptive cast counterfeits. This time, let's look at a cast that shouldn't fool any numismatist because it is so poorly made.

Think of it as the "poster coin" for an unfinished project. Nevertheless, this coin shows parts of a cast that are rarely seen. They must be removed before the coin can be passed off as genuine, unless as in the case here, the fake was represented as a minting error!

Cast coins are made using some type of mold. A genuine coin is encased in the mold material in order to copy its design, and then the mold is split apart to release it. This creates a two-piece mold bearing the impression of the obverse and reverse design and part of the edge.

When the two sections are joined to make the mold whole again (minus the genuine coin used as a model), there is a small seam left where they came together. Additionally, some holes are needed in the mold so that the metal used to form the casting can be injected while allowing the air inside the mold to escape. These are called "casting gates."

Casting has become very sophisticated over the years; yet, to my knowledge, this basic outline of the process has not changed. Can you think of a way to make a one-piece mold to produce a cast counterfeit coin? There will still be casting gates in the mold.

Once the faker has his mold, he is ready to make copies. In the "old" days, many cast counterfeits were made of soft alloys of tin and lead. That's because these metals are easily worked and have low melting points. Some readers may recall how easy it was to cast their own toy soldiers when they were young. So it was with coins.

A two-part mold made of brass or steel could be used over and over to make many copies without wearing out. You may have found some of these old fakes in a dealer's junk box. If you were to rub the edge of one of these base metal pieces across a sheet of white paper, it would leave a dull gray line.

As the need to make better-quality cast fakes arose, both the process and the equipment needed became more sophisticated and costly.

Let's examine the crudely cast nickel shown in the micrograph. Perhaps the first characteristic you'll notice is the small "finger" of metal protruding from the lower side of the 1970-S nickel. The projection on the edge, called a "sprue," is an artifact from a casting gate. It was formed by metal left in one of the casting gates after it cooled. Incidentally, collectors like to use the hours of a clock when referring to parts of a coin. So in this case, look between the 6 o'clock and 7 o'clock position, approximately at 6:30, to see the sprue.

Now, look at the entire right side of the cast. Do you see what looks like a flat, squished-out area protruding from the coin's edge adjacent to the date? This was formed when some of the metal injected into the mold seeped between the two parts where they were joined and then hardened. This is called "flash." Normally, the flash does not project this far from the rim. More often it is seen as a tiny ridge on the edge that runs around the coin's circumference. Note that there is hardly any seepage along the left side of the nickel.

For some reason, the faker did not finish this item. Usually the edge of a cast coin is filed flat in an attempt to remove all traces of the seam where the mold is joined. On coins having a reeded edge, this is more difficult. New edge reeding must be applied or the flash inside the grooves needs to be filed out so that no seam is visible. Hopefully, when you see what needs to be "fixed" on this fake you will be more aware of some characteristics that may be found on low-quality cast counterfeits.

Some words of caution: Genuine ancient coins can be found with an edge sprue; and many genuine Asian coins were cast rather than struck, so be wary of condemning every cast coin you encounter as a fake.

It's prudent to rely on a knowledgeable dealer who is a specialist in the field, or on one of the major grading services, when in doubt about a coin's authenticity.