what is the manufacturing date fo a colt diamondback serial number O72239
1977
Try looking it up at Proofhouse.com.
Made in 1967.Second year of production.
Post 1978. You will have to call Colt to narrow it down further.
Diamondback serial # D69679. was mfg'd in 1975. made about 1976
On the butt
I found a Colt diamondback with that serial number made in 1971.
made about 1977
Around 1968.
are you sure the '0' is not a 'D' ????? in the serial number
Around 1967.
1970