Lew - well, that answers the question of how they got the powder out! Mine inerted blanks had holes in them too - not so obvious as the ones on your rounds, but they are there. I never noticed them at all. Of course, my “ball” round does not, because they simply pulled the bullet out and dumped the powder.
I have no doubt now that these were not done by police for collectors. If so, the man-hours wasted on such a silly project on behalf of civilian collectors would have caused a stir! I can’t even believe the military would do such a thing! Absurd for such inconsequential cartridges. You want to teach about them and don’t want live rounds - fire them, draw pictures of them, take a photograph of them, section them, etc. Glue them to a board with the hole turned towards the board. Diozens of ways to do it more sensible that this. The Dutch Army Ordnance Corps must not have had much to occupy their time. It is funny, too, that they went to all the trouble to keep the blank crimps intact and fill in an unsightly hole in the case, and then pulled the bullet out of the ball round with a pair of pliers or with a collet-type bullet puller (terrible things for any purpose) that left four big scars on the bullet.
By the way, all three of your blanks are identical in headstamp to mine, if the lot number on the Geco one with plastic bullet is “14.” It kind of looks like “11” in your picture, but I think it might be “14” like mine.
Just started laughing so hard I could hardly type to finish this. I can’t get over the effort put into such a silly thing!