Proofhouse.com has Colt sn data.
That Colt police positive special with serial # 594826was manufactured in 1951.
about 1919
It was manufactured in 1920.
Good revolver.
what is the manufacture date of a .38 police positive special serial number b 81
1919-1922
1907-1909
About 1959
police positive special made about 1920
1927
Anything is possilble. The only way to know for sure is to get it lettered by Colt
About 1929. for a police positive special and 1935 for a police positive .38