I got the serial # from 54Mountain, and e-mailed it to my sister-in-law who works for Thompson Center, this is the reply:
"one of the gentlemen here said the gun was probably from around 1975 or thereabouts"
of course, T/C lost alot of their records in the big fire a few years back, so any details are lost, but the memories of people who worked there back then! too bad....