Your post made me think way back. This military gadget was a cam on the shoulder strap that could be quickly unlatched with either hand (it was placed on the front of the shoulder strap at about the nipple line. Once you popped that latch, that strap fell away and a simple shoulder shrug got rid of the other.

ai think it was issued sometime in the 1950s. I am not kidding when I call myself a geezer......