When minting goes right, nobody notices, but when it goes wrong, the result can grab your attention.

An error being offered in International Auction Galleries’ Oct. 22 and 23 sale, the firm’s 96th, is spectacular evidence of just how wrong the process can go.

When the Royal Australian Mint struck this 2017 Australian 20-cent coin, a wrong planchet was used. Such an error might not be so noticeable if only the wrong metal were used, but this wrong planchet presents more obvious and dramatic problem: it was a planchet intended for a Cook Islands $2 coin. (The RAM strikes circulating coins for other countries, including Cook Islands.)

The Cook Islands coin’s triangular aluminum bronze planchet (weighing 6.8 grams) is a far cry from the 20-cent coin’s expected standard round copper-nickel disc that weighs 11.3 grams and measures 28.65 millimeters in diameter.

The Cook Islands coin is supposed to weigh 7.55 grams and measures 26 millimeters in diameter on its sides.

The auction house calls this  a “superb and striking major decimal error of the highest importance and the only such example we have seen.”

Graded Mint State 64 by Professional Coin Grading Service, the “very rare if not unique” coin has an estimate of $12,000 to $14,000 Australian dollars ($7,809 to $9,110 U.S.).

Another error of note

Another error in the auction is almost as striking and notable.

This coin is a 2020 Donation dollar from Australia.

Its specifications are as expected, but the color was printed on the wrong side of the coin. In this case, the color intended for the reverse was overprinted in full on the obverse, completely obliterating the image of the now-late Queen Elizabeth II.

“A rare and spectacular mint error,” this “choice Uncirculated” coin has an estimate of $2,500 to $2,600 Australian ($1,627 to $1,692 U.S.).

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