I recently purchased an early post war Walther PP in .22 cal., serial number 159xxLR. It has the eagle over N nitro proof on the chamber and on the frame just after the serial. From the serial number, I am guessing the the pistol was manufactured in 1954/55. The Ulm proof started in 1952, I believe. Why would this pistol not have a Ulm antler proof on the chamber? There are no other markings on the gun other than the standard Walther PP markings on the left side of the slide. The finish is a high polish blue with a smooth trigger and very plain sights.