I am in possession of my Grandpa's .38 special CTG hand ejector. I was hoping someone could help me with a manufacturer date, or any other info, really. It's a 4" barrel, 4 screw, with serial number of B390243. Pretty positive it is pre-1955, which fits with my dad's recollection.
B390243 - The B indicates that it was shipped with a blued finish. I presume you got that number from the flat on the bottom of the barrel. If that same number is on the butt, the closest M&P SN I have listed is 3938xx which shipped in 2/1921. Pictures would help to confirm that ID.
Welcome to the Forum. Let's try to decypher what you have provided. My first guess is that you found the serial number on the flat under the barrel and if so, the B is not part of the number, but an indication that the gun was originally blued finish. 38 Special CTG stamp is also from the barrel, but CTG is simply an abbreviation for cartridge. If there is a screw in front of the trigger guard and four screws holding the sideplate in place, it is a 5 screw.
If the serial number is 390XXX, it would have shipped around 1922, but S&W did not log guns by manufacture date.