I think we’ve determined that cartridge #2 is a later date flare cartridge.
The pre-T65 cartridges can be found with both of the Winchester headstamps as well as the REM-UMC headstamp. Most with the AP bullet use the 165 grain M2 AP bullet with the cannalure. The later AP bullet with the one smooth crimping groove is very definitely uncommon for the early cartridges. (I’m not even positive that the later bullet was available in 1945.)
Most that I have seen are loaded to approximately 2.785" and the crimp groove is exposed. So yours is a little short. But that does not mean that it is incorrect, only that it is not normally seen that way.
You have to examine everything very closely. Does it have a powder charge? The extractor goove looks shiney in your photograph. Is it just light reflection or has it been messed with? Is the primer appropriate for a SUPER SPEED case? Could it be one of those flare cartridge cases in which somebody has seated an AP bullet? Be suspicious of everything. These cartridges are easily faked.
If you are satisfied that everything is OK and that the person you got it from is honest and can verify it’s provenance, then you may have a legitimate early pre-T65 cartridge.
Beyond that, I can’t be of much help.