Nice find.....I found a Kilgore Kit Carson a few years back. I find lots of these type guns (mostly broke up Parts) in old school yards. Most of the time if you can dig a few of these guns you should be able to find parts of the old metal toy trucks and cars also.
Nice Find.
I recall the Cap guns I payed within the late 70's were Still made of metal (mostly) then sometime in the 80's they were made of plastic.
Id think late 60 's Early 70 ' looks to be well made.
Davers