raincrowe, what you have appears to be a #10 known as a Heavy Duty Jack. The old catalogs show it to be 3 11/16" which is might close to 3 3/4".
The cursive Queen City stamp was used 1937 -'45.
The handle material is some man made material, there was a material known as "gum fuddy" that was used in some old Case knives. This may be similar stuff.
I have a twin to the one you have shown in your post here on my desk. The #10 has half stops and would be a great knife to carry. There is also a #18 Heavy Duty Jack, same dimensions but the main blade is a spear point rather than the clip as your knife has.
Looking through the Queen catalogs, the #10 appears to have had a name change in the '71-'72 catalog, it was then referred to as a Farmer's Clip from then on into the early 80's.
Hope this helps.