I recently picked up some yellow-tip FN55 headstamped .45acp shotshells without a package. They are similar to the M15 purple tip shotshells, but show some differences (M15 on left):
On the M15 that I have, I measured 127gr of #8.5 birdshot, and on the FN cartridge I measured 130.5gr of #7.5 birdshot. Has anyone seen the original box or packaging for the FN cartridge, and does it have a military designation? Were they used just during the 1950’s or into the 60’s & 70’s?