A letter from Colt will get you started.
If you are looking for when made--see below: The Colt police positive .38 & banker's special with that serial # was made in 1940. The Colt police positive special & detective special with that serial # was made in 1930.
Depends on which Police positive with that serial number: Police positive special in 1919 Police positive .32 & target in 1922 Police positive .38 in 1928
Police positive special=1919, Police positive .32 & target-1920,or Police positive.38-1924
Depends on which police positive with sn 134551: Colt police positive special -1916 Colt police positive .32-1916 Colt police positive .38-1921
Colt police positive .38 in 1914. Police positive .32 in 1909. Police positive special in 1913. Take your pick.
Take your pick: Police positive .38 in 1916. Police positive special in1913 and Police positive .32 in 1911.
Depends on what police positive. A police positive .38 was 1905 , a police positive special was 1908 & a police positive .22 target model G & C was 1910 based on serial number 1655.
Per proofhouse.com, it was made in 1911 for a police positive special & a police positive .38
In 1926 for the police positive .38 and 1919 for the police positive special.
Colt police positive special in 1909, Police positive .38 in 1908
About 1929. for a police positive special and 1935 for a police positive .38
If it's a Police Positive 38 it would have been made in 1920. If it's a Police Positive Special it was made in 1915. A Police Positive .32, would be 1914.