Ok, this might be a bit esoteric but as I sporadically collect British Commonwealth Caribbean coins, I have a number of the 1968 Anguilla $25 silver proofs. Only one has a numbered counter stamp on the reverse (tails?) side and the rest with no markings. I do not think it by accident or added other than at the mint as it is just like those on the proof 1968 Anguilla $200 gold coin; I have only seen two of those in 20+ years but both had numbered counterstamps in the field just as the silver. Not a big deal, but simply that I noticed it on the one silver and had not seen it on the others I have seen on the internet. "Normal" 1968 $25: Counterstamped specimen: Number counter stamp on 1968 Gold $200: