Around 1917.
That model was produced in 1922.
Your Colt Lawman revolver was made in the year 1972.
Without a detailed description, someone would have to research every serial number of every model of revolver Colt ever made.
@ 1978
You can find out at Proofhouse.com
made about 1911
about 1918
1918
1923
About 1903.
Check the butt.
1916.