Anything is possilble. The only way to know for sure is to get it lettered by Colt
about 1919
1919-1922
It was manufactured in 1920.
1907-1909
About 1959
1927
Proofhouse.com has Colt sn data.
That Colt police positive special with serial # 594826was manufactured in 1951.
Yhe records I have show a Colt police positive .38 with that serial number as being made in 1908.
Your revolver was made in 1939. The Puerto Rico rollmark is especially interesting. All of the revolvers I've seen with that marking are Police Positive models, NOT the Police Positive Special. Two distinct models. You dont mention condition, which is the most important factor. The gun would be of value to a Colt revolver collector, but condition is everything. Can you send digital photos? sales@countrygunsmith.net
1957
1972