I originally had this round a little over 2 years ago, and ended up selling it to a friend in the US, and he happened to be selling his collection and I ended up getting it back from him recently!
I was never able to get and ID on it previously so thought I would give it another shot.
It looks like a typical 30x113mm DEFA or ADEN TP projectile from the outside, however it has an odd steel disk crimped into the bottom. When tapped it sounds like the disk is very thin, which I would guess means there is something inside. Body is made of steel, aluminum windshield and 4 even punch crimps holding in the disk.
The only markings are “INERT” in white ink on one side and the numbers “157 S 000” stamped faintly on the projectile body.
Possibly “blind load” projectile, or a weight inside to simulate the correct weight? Would be great to get an ID or country/manufacturer origin.
It originally came in a typical British brass 30x113 ADEN practice marked casing but it could very well be the wrong case.
Thank you very much,