jgstang67:
Now that changes things.
Your serial number is just 816035.
If the barrel is stamped ".38 S&W Special CTG" then you have a .38 Military & Police Model of 1905 4th Change manufactured in 1941 or 1942. This lacks the hammer block safety, which was introduced on late 1944. I would leave the chamber under the hammer empty if the gun is being kept loaded or carried. It does have an earlier internal safety, but this can fail when the gun is dropped - a fatality on a naval vessel during WWII lead to the development of the modern hammer block. The '4th Change' refers to the 4th design change on this model, the early internal safety was part of that design change.
Quality of the steel on this gun would still be good, so limited use of PlusP ammo should be fine.
If the barrel is stamped ".38 S&W CTG" then you have a British Service Revolver manufactured in 1941 or 1942. This was the Model of 1905 4th Change manufactured for England during World War II to chamber their .380 revolver service cartridge, which was based on the early .38 S&W cartridge.
After World War II a lot of these guns were re-imported into the USA, the chambers were bored out to accept .38 Special (a longer cartridge) and they were sold by mail order houses. A converted gun will tend to bulge .38 special brass as the .38 S&W chambers are wider at the rim than the .38 special cartridge.
If the gun lacks English proof marks it is probably originally a .38 special. Another test is to look at the grips, if they are smooth walnut then it was probably a .38 S&W at one time. If they are checkered walnut with S&W medallions then it was probably a .38 Special. Also try inserting a .38 special cartridge half an inch into the chamber - if you can wiggle it from side to side it may be a .38 S&W that has been bored out. If it is a tight chamber it is an original .38 Special. If the .38 special wont chamber then it is an original .38 S&W.
Converted guns have minimal value and it would be prudent to stick to standard pressure ammunition to avoid split cases and gas escaping. An unconverted .38 S&W will have a value lower than an unconverted .38 Special due to the high cost and low availability of ammunition.
Oh, and I have no clue who stamped a P on it.