With respect to the OP knife/stamp - since it has Boulder, Colo. in the stamp, the knife was made before 1973, and since it has U.S.A. in the stamp, post-WW2. Without a look at any stamps on the pile side or on the tangs of any secondary blades, it can't be boiled down any closer than that.
Western bought the property in Longmont in 1972 and with an eye to the future, dropped "BOULDER, COLO." starting in 1973. They didn't move to Longmont in 1978, IIRC. So the stamp went from WESTERN over BOULDER, COLO. over U.S.A. to simply WESTERN over U.S.A. at that time.
On Western stamps. I am in the final stages of putting together a new WESTERN FIXED BLADE stamps chart,............... which I believe is up to 23 or 24 stamps - that's JUST fixed blades. I haven't even thought about the complexity of folders. Probably just as many variations. The "standard Western tang stamp chart" with only 11 stamps is sorely lacking for covering both fixed blades and folders over a 93 year period.