Manx and UK 10ps were then downsized and offered for sale at Royal Wootton Bassett's RWB Auctions.
Prior to the introduction of standard coins into circulation, the pre-production trial coins were designed to assist companies in calibrating their vending machines and other currency systems.
The seller kept the artifacts for over 30 years after requesting them from the Isle of Man Treasury.
Less than 200 of these pieces are believed to have been produced, and because they have hardly ever been put up for sale, collectors highly value them.
Three difficult-to-identify characteristics distinguish the uncommon 1992 Isle of Man coins.
Ordinary 1992 Manx 10ps contain the letters 'PM' beneath the Queen's neck, but there are no initials beneath her face.
The '9's in the date have rounded tails instead of the sharp tails found on regular 10ps. The letters 'AA' are located on the top of the inverted foot of the tails side triskeles motif.
An ancient emblem connected to the Isle of Man, the triskeles or triskelion is sometimes depicted as a three-legged spiral. Manx coins, which are well-liked by coin collectors due to their distinctive designs, frequently display it.
A rare one may easily be confused for a regular British 10p at first glance because they are the same size as UK coins, which Brits occasionally find in their change.
Only a few hundred of these Manx coins were ever produced, according to Christopher Collects, a modern coin specialist with RWB Auctions.
Because of this, they are far more rare than coins like the Kew Gardens or Salmon 50ps that you may be familiar with.