Center part of the die is a separate piece with just the '50c' on (inserted through a hole in the middle of the main die). Get's hotter than the rest of the block so it's the first part which will melt more foil.
Leave it a fraction longer and it will look like the version in Roy Klein's hand in the OP.

Get a whole box of these and you'll find all the variations inbetween.
Industrial hotstamping is a pretty rough and ready process. We are only talking about 100 milliseconds dwell difference between no stamp and obliteration.

10% of these end up in the trash as they are too bad either way. Variation occurs through a run because once you've heated the die to the correct temp to start, it will continue to get a tiny fraction hotter if it's in use for an hour or so, or someone forgets to turn it off during toilet or cigarette break etc. etc.
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