I believe the knife you refer to is a M1942 Bolo Knife (United States Navy Hospital Corpsman).

They use to be very common in surplus stores. I bought one as a kid and tried to sharpen it, but the edge was too thick to take any kind of edge.

I have found nothing of there use or intended use (but would be only slightly less useful than an entrenching tool (the WWII/Korea/early Viet Nam wood and steel variety) as last ditch hand to hand fighting implement.

(My battalion(2/7) Sergeant Major earned a Silver Star in Viet Nam for effectively demonstrating the proper use of an entrenching tool to several Viet Cong.)