A couple of days ago I’d paid a visit to my friend - a gunbroker in my favorite gun store. He showed me a 23x152B cartridge, which, I suppose, was API, judging by the shell shape. But the shell was rusty and its point color marking was long gone. I wish to ask, if there is someone familiar with this type of rounds, is there a possibility to tell API from, say, TP (which is very similar in shape) without destroing the windcap?
The stamp on the shell body was 15-33 in double circle-85П
The headstamp on the steel case was - 12 o’clock: 87, 6 o’clock: * (six point asterisk).