Picked up a few boxes of some sort of surplus 9mm that I am curious about. It is in brown square boxes of 64 rounds and has no useful information printed on the box. Head stamp merely has 9mm and a two digit number which appears to be year of manufacture. Some of the ammo is '40' and some '43', assumed to be 1940 and 1943. The only thing I have located similar to it is identical, but stamped ENGLAND on the box and described as hot British submachine gun ammo. The date stamps on it were in the same range as mine.

I assume this 9mm is corrosive which doesn't bother me too much. But, I want to use it in a P38 Walther from February of 1945 (not collector grade) and these pistols are said to be subject to damage with hot ammo. In fact, Walther folks suggest using only the mildest loads.

Anyone have good information about it. My ammo: