Just for the record, the earliest one of these dummies I have encountered is the P EX 21. I have one with four holes in the case. My earliest undrilled one is P EX 22. My latest date undrilled on is P EX 37, which fits in with the 1938 date for the drilling of holes in new production, given us by Peelen, very well.
They actually went back and drilled the holes in dummy rounds 15 or 16 years after they were actually manufactured. Does anyone know if there was a recall of already issued 9 mm Exerzierpatronen for the purpose of drilling the holes, or was the retro-drilling of the holes of the pre-1938 dummies done only on unissued, warehouse stock?
At any rate, it was an incomplete after-action, as these dummies with no holes in the case, which not found as often as those with the four holes, are not particularly scarce. Many of them survived without being drilled.