Proofhouse.com has Colt sn data.
If you call Colt with the sn, they will tell you.
That Colt cobra was made in 1976.
Colt data at Proofhouse.com
check at: proofhouse.com/colt/index.html
1970
1965
1965
Proofhouse.com has Colt sn data.
That sn doesn't fall in the Cobra range.
1967
1956
Proofhouse.com has Colt serial numbers you can look up.