This month I'm writing a little bit about the riddler. No ... the article has nothing to do with Batman and Robin. Rather, the riddler is a device utilized in the manufacturing of coins. It's a mechanical unit that goes a long way in keeping many of those neat error coins out of our hands. It's part of the mint production system which literally screens coins and separates the good pieces from the bad. Now I realize that "good" and "bad" are matters of perspective between the mint and the coin collector. To the mint, the "good" coins are error-free. Conversely, many coin collectors prefer the "bad" or "error" coins. So, just what is the riddler device and how does it function?

For the mass production of circulating coins, the U.S. Mint utilizes a system of elongated, vibrating screens or sifts - called riddlers - to separate the errors from the good pieces. These riddler screens/sifts are long, flat devices which resemble a wide strip of coin metal after the planchets have been punched out. The holes in these riddler screens are of various sizes depending on the size of the coins or planchets being screened or sifted at the time. The riddlers resemble a conveyor belt with raised sides, but they don't move in conveyor fashion. The riddlers vibrate very strongly so as to cause the coins or blanks which pass over them to bounce around on the screen, and over the holes, to separate the good pieces from the errors. The riddlers are angled/tilted downward so that the vibrating coins or planchets bounce along from one end of the screen to the other. The riddler operation is entirely mechanical. The coins or planchets are fed onto the riddler device at one end, and the separated products (errors and good pieces) are dropped into bins or boxes at the other end.

The riddler screens are utilized in combination; that is to say, they're stacked on top of each other. In other words, there are usually three levels of riddler screens which are used simultaneously. The three levels are stacked, one above the other, and are each separated by several inches of height. All three screens vibrate vigorously. The coins or blanks or planchets are fed onto the top screen. The holes in the top screen are sized to permit only proper sized coins, or undersized pieces, to fall through the holes of the vibrating screen. Thus, all oversized coins and larger pieces (maybe a piece of errant planchet strip) are retained on the top screen, allowing all of the proper sized coins and smaller pieces to fall through to the second level.

The second, or mid-level screen has holes which are slightly smaller than the proper size for the coins being screened at the time. Thus, as the coins or planchets vibrate along this middle screen, only the undersized coins or pieces fall through the holes. The proper size pieces are retained at the mid-level and eventually fall off the end of the tilted, mid-level screen into a bin or onto a conveyor belt. In theory, only the perfectly shaped coins or planchets fall into the bin or onto the conveyor for further processing.

The lowest level screen is actually more of a closed-end catch basin. It, too, has holes, but the holes are fairly small and merely feed the vibrating, undersized pieces into boxes below the riddler device. The undersized coins, planchets and pieces which are caught in these boxes below the riddler unit are then gathered and sent back to be re-melted. Actually, the top riddler screen is also a closed-end catch basin. As you recall, it retains all of the oversized pieces. These oversized pieces, too, are eventually gathered from this top screen/box and sent back to be re-melted. Only the middle riddler screen empties into a bin or onto a conveyor belt from its opened-end, catching all of the proper shaped coins or planchets for further processing.

Not to be redundant, but as an overview, try to visualize it this way. Three long layers of screens or sifts - all are slightly tilted - all vibrate vigorously - all stacked a few inches above each other. The top layer is boxed, closed on all four sides. It has holes the size of the coins being screened. The proper size and undersize coins and pieces fall though to the middle layer screen. The oversized coins and pieces are caught/trapped in this top layer to be re-melted. The middle layer screen has holes smaller than the coins or blanks being sized. The vibration causes the undersize coins and pieces to fall through the holes to the lowest level/third level screen. The proper size coins or planchets from the middle level vibrate off the open end of this mid-level screen and fall into a bin or onto a conveyor for further processing. The lowest level of the riddler is also boxed/closed on all sides and has smaller holes yet. It vibrates the undersize coins and pieces into catch bins below the riddler machine, where they're eventually gathered for re-melting.

I've somewhat interchangeably used the terms coins, blanks and planchets in this description of the riddler devices. That's because the riddlers are used to separate errors at several stages along the production process. The first use is on the blanks which have been punched from the coin metal strip. The second riddler sifting is on the planchets after they've been through the upset mill (unstruck coins are "blanks" until they receive their raised edges in the upset mill, and then they're called "planchets"). The third use of the riddler is after the planchets have been annealed, washed and burnished and are ready for striking. The fourth use is to screen/sift the struck coins just after they leave the coinage presses. And finally, the riddlers are used one more time just before the coins are sealed into their storage/shipping containers by weight.

With the blanks, planchets and coins going through the riddler devices so many times (each time catching errors that were previously missed - or catching new errors as a result of subsequent stages in the coining process) it's really a wonder that any error coins whatsoever escape the Mint and enter into commercial channels where they can eventually come into the possession of dealers and collectors. But I'm sure glad some of them do!! I guess it's the law of averages. The Mint produces such a tremendous volume that sometimes a few errors are just bound to escape.

Best Regards,

Ralph J. Huntzinger
WINS President