Paul, Welcome to the forum. The markings indicate Schutzpolizei Arnsberg District duty locations 4 and 2 respectively. Weapon #38 and weapon #51.I'm not certain of the meaning of 2. and 5. in front of the weapon #s. It's an Arnsberg Police issue pistol. Unit marking was ordered to cease in 1937. You have a desirable police luger. Try to post some photos. we would like to see this one.
Ron
Ron