Maybe they just used the small British 5p coins to calibrate machines. What makes you think a 1991 5p would have been issued? To complete the date run or something like that?
"For by telling them of many things without teaching them you will make them seem to know much, while for the most part they know nothing"
-Plato
In 1985, the Irish government minted approx. 500 20p coins dated 1985 to calibrate and test all the vending machines in Ireland. These coins were used to test re-calibrated public telephones, vending machines and parking meters throughout Ireland - a huge logistical task. In due course, the new 20p was released in 1986. All of these 1985 test coins should have been handed back to the authorities when the testing was finished - approx. a dozen have been found.
In 1992, the Irish government minted 500 new design (smaller) 10p coins dated 1992 to calibrate and test all the vending machines in Ireland. In due course, the new design 10p was released in 1993. All of these 1992 test coins should have been handed back to the authorities when the testing was finished - only 2 have been found.
In between these two issues, a new design (smaller) 5p coin was issued dated 1992. The last large size 5p was issued on 1990 and the new smaller sized 5p was issued in 1992. It makes complete sense that a batch of test coins would have been minted and used for testing beforehand - none have been found.
I do not think a GB 5p would have been a suitable substitute since it was thicker and smaller, although both coins were the same weight.
Irish 5p (small)
diameter = 18.5 mm
thickness = 1.67 mm
weight = 3.25 g
GB 5p (small) (1990–present)
diameter = 18.00 mm
thickness = 1.89 mm
weight = 3.25 g
I see, thanks for letting me know I always assumed they had the same specifications, haha. However it would indeed be logical that a number of 5p's was minted in 1991. But maybe the coins minted in 1991 didn't bear the year 1991, but 1992 instead? The same thing also happened in many of the first 12 euro countries. Coins dated 2002 were already minted from 1999 to 2001, in Germany and Austria for example. I thought it had something to do with the fact that some countries have laws that require them to mark coins with the actual date of when they were minted, rather than the date on which they were released into circulation. My country for example is among those countries and that's why we have eurocoins dated 1999 while we didn't actually use them in 1999.
"For by telling them of many things without teaching them you will make them seem to know much, while for the most part they know nothing"
-Plato
If the Irish 10p and 20p coins were minted with the year before they were released, it is unlikely that they would have broken this rule for the 5p.
However, the 5p was not released until June 1992, so they would have had 5 months to do the work.
Would 5 months have been enough to re-calibrate and test every public phonebox, parking meter, and vending machine in Ireland?
The official papers detailing what happened in 1985 were recently released.
Perhaps we will find out more when information becomes avaiailble for what happened in 1991.
