Look on the butt.
Impossible to answer because you did provide any information about the revolver or the serial number.
What model .38?
Model 10
On the butt.
SN's were not required before 1968
1911
50-200
Early 80s
You can either call Colt or look it up at Proofhouse.com
there are far to many #s to be a proper serial #
1967