As a point of reference for 'next time' … Could some kind soul please post a copy of Martin Cleeve's article on Gauge Pins
Model Engineer, Vol.114, No. 2871, 31 May 1956
This obviously pre-dates the 50p coin, and is, I think, the first place I saw reference to the occasional non-circularity of Silver Steel. … There may [of course] be earlier references, but this would make a good benchmark.
The underlying geometry was already well known; from the similar effect sometimes produced by a drill in thin sheet metal.
MichaelG.