That would have to be a .38 Military & Police. It probably shipped in 1950. Model numbers were not used until 1957, but this model would eventually be designated the Model 10. Collectors will sometimes identify specimens like this one as a Pre-10.
If it has four screws in the sideplate (which it should at this time), then it is a five-screw gun. The rearmost screw in the sideplate is probably covered by the stocks. The screw in front of the trigger guard is counted too.