These were available from P&S Sales catalog in the 1960s. I bought allot of stuff from P&S sales and thought about acquiring one of these "trench knives" because I recognized that they were made from the blade of the M1913 saber. I thought at the time they were something put together by someone to use the blades and discounted the idea these were actually something done by the government for issue. As I recall the illustration in the catalog and the collector guide showed a rather plain wood handle and a knuckle bow guard. I wish I had bought a half dozen at the time they were available from P&S Sales. I have subsequently seen a couple of these at gun shows.
Apparently the blades were cut into three sections, so there was 3 variations of the blades. The section with the markings and the center section had to be ground to a point. The tip section and center section had to be ground to create the tang.
Your example has a different handle and guard (similar to the Fairborn knife) than those I recall seeing, so yours may be a one of a kind custom job.