1956
1954-58
Between 1971-1973.
1956 570,813 shipped 7/21/1956
The JC Higgins Model 80 was actually made by High Standard for Sears, and is the same as the M101 Duramatic pistol. Made from 1957 through 1961/62. These can be bought on the use marked for $200-$250.
No way to know without trying.
Contact High Standard with the Serial Number and they will tell you when it was manufactured.
100-1000 USD
1,000,000,000
1970
Yes, they made that model
1974