Erik M:
You have a .38 Military & Police Postwar (Transitional Model) manufactured between September 1945 & October 1947.
This is considered a treansitional Model between the pre-war .38 Military & Police Model of 1905 4th change and the .38 Military & Police (Postwar) that became the Model 10. It should have the prewar Long Action, with the hammer having a longer throw than a Model 10. This gives a smoother trigger pull than the current Short Action. It wil also have the internal hammer block safety developed during WWII, hence the S prefix to the serial number, standing for safety.
The .38 Military & Police Postwar had the internal hammer block and the new short action, from roughly August 1948, IIRC. In 1957 it was designated the Model 10. Prior to that there were no model numbers, just model names that were not stamped on the guns.
TL,DR: 1945 to 1947, probably early 47, safe to load six, should be safe with any current standard pressure or PlusP ammo, should have a nice trigger, use the how to check out a revolver sticky at the top of this forum to make sure its safe to fire. Some collector interest, but only worth around $350 in excellent condition.
Hope this helps.