Model number will be inside the crane area when you open the cylinder.
It could be one of eleven models. You fail to provide caliber or barrel length and ALL markings that would narrow down which of the eleven;1973
1954.
1955
and the model is..................................
.22 cal
Around 1955.
1961-1962
Go to proofhouse.com and take your pick.
1977
1969
Impossible to answer without a serial number.
No serial number given = no answer.