Hi Hal,
* Mauser military P.08's were S/N'd in blocks of 10,000 pistols. First block was all numeric digits (1-10000); hence called the no suffix block by collectors. The 2nd block of 10,000 included a lower case, script letter "a" (1a-10000a), 3rd block was the "b" suffix block, and so on.
* Mauser began the Army P.08 contract in 1934("K" Date) with the first use of the no suffix block S/N's. By the end of 1937, they had run through the entire alphabet suffix letters ("j" was not used). Unlike other time periods, contractors, & contracts, Mauser kept right on numbering in sequence despite the end of a year (chamber date). So, they ended the 1937 production with the "z" block, no suffix block & into the "a" block.
* Jan Still gives the S/N range for a 1938 chamber dated, S/42(Mauser) coded P.08 as 400b-4500n based on S/N's reported as of the 1988 publication date of his book Third Reich Lugers (Pg. 40). The range is essentially the same today with minor exceptions.
* Your "h" or "k" block fits neatly into this range. It is an important part of the S/N identification of this pistol when coupled with the chamber date, Manufacturer, caliber, & barrel length description. This, then, uniquely ID your example from others which may have the same numeric S/N digits; but be of a different S/N block, etc.
* Your current magazine would be contemporary to a later '41 or '42 Mauser P.08. It is an improved, strengthen design likely bearing the code "fxo".
* The original matching magazine issued with your pistol would have been a coiled spring, blue tubed, side pinned aluminum based plug equiped, rolled/crimped sheet metal magazine bearing the pistol's full numeric S/N complete with suffix letter and the Army inspector's stick eagle/63 or sE/83 acceptance mark similar to what is located on the right receiver of your pistol. The 2nd mag would have been marked same as the above and also have a "+" to indicate it was the reserve( spare) mag.
* Trust this helps.
OBTW: Hiya, Don!! Good to see you at the keyboard posting again. I haven't forgot you. Will voice mail you soon.