Coin Monday: "A Bonded-Mated Pair"

March 1, 2010

Written by John Dale

“A bonded-mated pair.” While it may sound like the subject of a pulp magazine cover in the next Illustration Art catalog, it’s actually a coin term, used to refer to a particular class of error. A “mated pair” is a set of two coins united by a common strike; a “bonded-mated pair” is a mated pair in which the two coins were fused together instead of separating. This is what happened to the bonded-mated pair of 1972-S proof cents coming up for auction in the March 2010 Fort Worth Official ANA Auction.

So that’s the answer to the first question: “What the heck is that?” Now for the second: “What the heck happened to it?” After all, most of the fun in error collecting comes from imagining what happened!

I described a mated pair as a set of two coins united by a common strike. More specifically, imagine one coin being struck. The planchet goes between the dies, the moving die goes down and strikes the planchet with a ton of force. Out pops a coin, which then leaves the dies. Another planchet takes its place.

But what happens when the newly struck coin doesn’t get out of the way? It can stick to one of the dies, leading to a brockage error, like this dime I wrote about back in June 2009. Or the newly struck coin could get partway out of the dies, but not completely. It lands under or on top of the next planchet, the dies come down, and suddenly there are two coins which share one impression from the dies.

Usually the two coins separate from each other after the strike. Often they are split up, with one being caught in an inspection and never leaving the mint, for example. Owning a mated pair, or both halves of a common strike, is far more desirable than having just one of the pieces.

A bonded-mated pair takes the idea of a mated pair one step further. Instead of separating, the mated pair is bonded together by the common strike. Most bonded-mated pairs never get out into the world; they’re ludicrously easy to spot in a hand-inspection, and several automated systems are designed specifically to weed out misshapen oddities like this one. Interestingly enough, this error is also a proof bonded-mated pair, and all proofs are supposed to be hand-inspected at least once before they head out the door! Makes you wonder… [Then you realize that this thing was made in the early 1970s in San Francisco, and it all makes sense. – Noah]

What’s most dramatic about this error is how it’s bent. The photographs, as great as they are, can’t do justice to how truly three-dimensional the error is. The two coins form an angle nearly 45 degrees from the horizontal, like the sides of a chevron or the two halves of a book held open as a reader searches for a page. While this error, like all the best, leaves a few unresolved questions, it does offer many insights, and more importantly, a solid jumping-off point for wild speculation. So in both speculating and bidding, have at it!

-- John Dale Beety