Long-time lurker, but first post on AAPK....
The knife and sheath are both authentic WW2 vintage Western items.
The pre-WW2 G46 series had the "mushroom" pommel, as I call it. The first documented use of the bird beak pommel by Western is in the 1931 catalog reprints, where Western called it a "curved, metal end knob". Hereafter, BB will mean "bird beak".
During WW2, the G46 series morphed into two styles. One style had the BB pommel and the other style had the flat typically associated with the 1219C2/USN MK2/some versions of the USN MK1.
First, the BB knives...
From 1931 to 1941, the G46-4 (with a 4-1/4" blade), G46-5 and G46-6 had mushroom shaped pommels.
The BB G46s came in 2 blade lengths - 5" and 6". The G46-4 production ceased during the war and was never brought back after the war. Both had fullers. Western terminology remained G46-5 and G46-6, the same as their their pre-war designations. At some point in time, the knives were dubbed the Baby Shark and Shark by someone.
The early versions had aluminum BB pommels (as did the L76 and L77 Commando Dagger and Commando Knife) and the very earliest had brass guards, essentially stock on hand. With wartime rationing/restrictions on the use of aluminum, the BBs started using a brown swirled plastic for pommels. Some guards were steel and other used the same brown swirl plastic.
Without measuring the blades, a Shark can always be recognized by the lanyard hole in the pommel. The Baby Shark never had one.
I have always assumed that the plastic guard knives were late war production. Although I have no documentation on that, I once saw a picture on line (and stupidly did not copy it) of a case of plastic pommel/guard Baby Sharks was found still n the factory paper. There was a picture of a 1945 shipping date on the box.
On to the flat pommel knives.
There were 3 G46 flat pommel knives and 2 L71 flat pommel knives.
The Gs were the G46-5, G46-6 and G46-8, with 5". 6" and 8" blades respectively. The L71s came with 5" and 6" blades. In The Knife Makers Who Went West (TKMWWW), on the single 1945 page depicting the Western war year knives, the L71, aka the "Seabees" knife is listed as having a 5" blade. I call these the L71-5 and L71-6, although Western never designated them that. The L71s and the G46-5s were Western's equivalent of the USN MK1.
The WW2 G46s, BB or flat pommel, had fullers in the blades. The L71s were flat grind, no fullers. The reason I say there were both 5" and 6" L71 versions made is because I own some of each. TKMWWW, while a good reference, has errors. This is one of them.
Western never had a DoN contract to make the USN MK1 or MK2. But they made equivalent anyway and sold many thousands of knives to the military, primarily the Navy and Marines due to the relative closeness of Boulder to the west coast - an overnight train trip allowed for rapid delivery. WW2 purchasing was less rigid than peace-time ordering. Units had discretionary funds and would buy the knives they wanted. The G46-8 was very popular for both its slightly longer 8" blade and the fact that the tangs didn't snap as easily as those on the 1219C2/USN MK2.
So, in a nutshell - fullers = G46s, flat grind = L71.
Terry
) so that my nephew will KNOW how badly he is getting ripped off if he sells them. 
The "stuff" I accumulated from 1977 through about 2001 is less properly documented. 
