Dave - They do not show up much. The concept of a proof load in a blank was something new to me when I acquired a box of them. I haven’t check my box to see if it is the same as Bob’s, but it is Geco also. At the time I acquired it, which is only about a couple of years ago, we had never heard of such a thing. In fact, it was even unknown to Bill Woodin, which surprised me. Happily, the box was full so there were some to go around.
One of the German collectors explained to me why they had to make some blank cartridge proof loads, since German law did not exempt the little blank/gas autos from the proofing laws.
I just went down and got my box. It is the same as Bob’s I would guess. ON mine, the original caliber has been changed bu blotting out the number “8” for the 8mm Platzpatrone, which I have not seen in a proof load but obviously exists since this box was originally printed for it, and stamping “6.35” above it. The box label does not actually say “squared” anywhere - I guess Bob was pre-interpreting that part of it, unless his does say it.
Mine had cartridges with two different headstamps in it. One is just “Geco 6.35” while the other
is headstamped “L Geco L 635”. The “L” in both instances is upside down and backward, making the date code for 1966. The primers are lacquered all black, and the rims are knurled.
In the case of each of the two headstamps, there are two bullet-shape variations to the white, hard-wax bullets. One pretty much duplicates the standard ogive of a FMJ RN 6.35 mm bullet.
The other has straighter sides up to with a mm or so of the tip, and then curves over in a dull-pointed tip. Four variations in one box! Fun!