The butt of the weapon.
Based on proofhouse.com the 1977 colt cobras shows serial numbers 60001R - 71400R & 1978 as just 63401R????????
Your colt cobra was made in 1966.
colt cobra 38 special serial number 139350
Early 1969.
1967
Proofhouse.com has Colt sn data.
1969/1970
1974
Impossible to answer without the serial number.
Proofhouse.com has Colt sn data.
Can't be answered without the serial number. You need to call Colt.
56 yrs old