Recently ran up on a Mauser P.38 with mismatched numbers, and wanted some assistance. Left side of slide shows "P.38" and "byf 43" - so far so good. But the serial number on the slide seems to be short to me. It's only two numbers, followed by a script "a". Same two numbers and script "a" on the frame, along with the eagle over 135 acceptance stamp. The barrel shows four numbers followed by a script "b", and the locking block shows three numbers and a script "b". So the big question: Were there ever 3-digit serial numbers? My understanding was that it was always four numbers, followed by a letter code. Is this a normal marking for the start of a block? (Did they just leave off the leading zeros?) Is it a mistake? I welcome the opinions of you P.38 experts.