1972.
35yrs
your marlin/glenfield was made in 1974.
20626860
With the serial number that you have supplied,your Marlin(Glenfield) rifle was made in the year 1980.
your glenfield was made in 1968.
Marlin made the Glenfield firearms, not Winchester.
1980.
Your Glenfield model 60 was produced in 1989.
With the serial number that you have supplied,your Glenfield rifle was made in the year 1973.
I found the value of a Marlin/Glenfield (similar serial) to be at about $2,700. I'm looking too, but that's the price I was able to find.
1978
1975