It may be German. Factory codes "04" and "05" are often German. So it may be German 1988, factory 04 ammunition.
I also have some of it around here somewhere. It came packed in "blister packs" of 10 rounds each. My memory recalls it being available in the 80's also. Definitely East German, and corrosive.
The coating is similar to the newer Wolf gray polycoat. I'm kind of curious what these will penetrate.
I saw expended rounds all over the place on the Military ranges in West Germany during the late 70's.
Penetration? Virtually none...The round was specifically designed with "short range" and no penetration. The bullet itself is a powdered metal in a brittle plastic binder, designed to disintegrate on contact with nearly any obstacle. If my memory serves me the round was limited to something like 25 meters or so. Edit: O.K. now you guys have done it....I went to the basement and found the ammo. First it does come packed in 10 round "blister packs, DEFINATLY German! My cases are steel , however, the have the traditional lacquer finish in the typical greenish color of the time. On checking the bullet itself, scratching under the surface reveals that the ones I have are a Brass jacket, rather than the steel reported above. The pack itself has a "yellowish" colored blister with a yellow colored paper backing. Embossed into the plastic is... 10 Stuck M-43 Ub -2- The casing themselves are marked as 05 over 86. I hope this helps.