I was surprised when I found I didn't have another stamp to compare this to. Well, today I found them hidden in a stock book - 3 complete sets of the non-Olympic sports, abd lo and behold, it looks like I have another copy of this variety. Pictures follow:


For comparison, here is the detail image from previously.

It is rather odd that these do not look like the same retouch. Is there any possibility that this comes from a different position on the sheet? There do seem to be significant differences in the black line that separates the retouched grey area from the yellow area above it. Alternatively, there could have been intermediate stages of this variety.
Frank.