Your pistol is correctly identified as a Type 4 Sauer. Production of this varient began in late 1943. The legand on the left side of the slide was changed to read simply "Cal 7.65" and the right legand was eliminated. The finish was milled, with polishing eliminated to speed producton. This period was the most intensive of all wartime production for Sauer.The thumb safety was dropped from production about SN 470000, creating the Type 4a. Your Sauer was produced in late 1944 or early 1945. The lack of a WaA or E/C on the left side of the trigger guard would indicate this gun was of commercal manufacture, and probably purchased by an officer (the officers had to provide their own sidearms and holsters). This would also explain the unmarked holster. Both Heer officers and the Luftwaffe used brown holsters, so the branch is anybodies guess. The grips had no fiber reinforcement, and so are VERY brittle and easily broken. Take care with them, as originals are un-replaceable! Hope any of this helps.