Gut reaction is .... Western.

Note - edited to add pics
While MOST of the fixed blades Western produced from 1934 to 1990 were split-tangs, there were a significant number of models produced with "standard" full tang blades --- Bx54 Bushman, W49, W47, W45, W43, Westmark 701, 702, 702, all of the W-series fillet knives.
Here's my reasoning.
Western had a contract w/ Monkey Wards to make Western Field knives during the 1950s. This conclusion is based on split tang WF knives.
Western had a short-lived re-introduction of the WEST-CUT line with the K1/K2/K3/K5/645 knives in 1958. (Short-lived as they were NOT in the 1960 catalog pages.) The "K" knives were NOT made using split-tang. K1/K2/K3 were B&T knives, similar in size and shape to the (L/F) 58/48A/48B models.
The K1 = similar to the L58
And I can't find my K2 pic

- but it looks like an L48A
The K3 = similar to the L48B
The K5 is similar in size/shape of the 66 knives (L66/F66) of the same era.
The 645 was a 2 pin hunter resembling other companies 1940s/1950s hunters.
Without a flat picture with a ruler to show profile and blade/knife length clearly, it APPEARS that your knife is about 9" OAL. If so, it would be a twin sister to the K1 - 9-3/8" OAL, which was a single pin, non-split-tang B&T. If it's about 8" OAL, the K2 and if a tad over 7", the K3.
On a side note - I read somewhere once (and now can't find my copy of the info) that the Camillus 1005, 1006 and 1007 single pin, full tang fixed blades were made by Western. Also, if you compare the 1970s/1980s Camillus wood handled fillet knives to Western's fillet knives of the same era, they sure do resemble each other.
