Behold my most prized possession. Here's literally the only info I found online
HAMDEN NON-CATALOG STYLE 11: 7 inch, Clip Point, Full Tang Blade; With Steel Guard; Nickel-Chrome Moly Steel; 1-1/2 Sharpened Edges; Rock Maple Standard Type Handle with Poured Lead Rivets; Has Extended Tang; Has Lanyard Hole in Handle;
The Style 11 is basically a Style 9 Marine model with an added crossguard. Probably made for those GIs who wanted a knife that wouldn't allow a wet or slippery hand to slide forward onto the blade under a forceful thrust.