Not recommended. Seek the help of a gunsmith
Colt 38 special police edition s/n 18759
In 1926 for the police positive .38 and 1919 for the police positive special.
Official Police ser numbers started at 513216 in 1927. I believe you have a Police Positive Special from 1921. It was chambered in .32 Colt, .32 New Police, .38 New Police and .38 S&W, .32-20 and .38 Special.
When you release the catch to the cylinder you should see the serial number stamped on the crane at the swivel.
Colt police positive .38 was made in 1919 and Colt police positive special was made in 1914.
In short, no. The pressure rating of the barrel of a .38 gun will not handle .357 pressures reliably. Even if you could somehow find a cylinder that would fit, it would eventually blow up in your face.
It was made in 1924.
Depends on your intended use.
That Colt police positive .38 special was produced in 1919. (162000-189999)
That Colt .38 special police was produced in 1951. (571500 - 607399)
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.
Police positive .38 with that serial number was made in 1908.The police positive special with that number was made in 1910.