Originally Posted by
Scott Gahimer
I think the short toe is primarily what to look for...but a well-formed toe that has been filed, shortened or squared-off. If you find a non-lanyard loop with an original, well-formed and rounded toe...then, it may be a Remington Arms-UMC mag. You might also compare finish and other characteristics to other known Colt mags and look for differences. I don't think it's all black and white, as the mags were supposedly made to the same specs and were supposed to be fully interchangeable.
There were 21,676 Rem-UMC pistols made in 1918-1919. That would mean there were probably less than 65K total mags for new pistols, plus whatever mags they may have produced for field service replacement purposes. Compare that to the Colt numbers and chances are pretty slim of finding a UMC mag. The majority of mags believed to be UMC are probably Colt.