They both look like Singer 31-15 machines to me. It was a very popular machine for the Navy, as well as the other branches of the service during the mid-40s.
I’ve seen photos of other military machines that were similar, but built into a heavy wood box for portability. The box looked sturdy enough to drop by parachute without hurting the machine. I’m not sure that they ever did that, but it looked possible.
CD in Oklahoma