[John Sabato]

The 5994 n is your serial number. The letter suffix is a part of the serial number but only appears on the front of the frame above the trigger guard. The 4 digit number on the side of the upper receiver does not normally have the suffix letter. The 2 digit numbers 94 on all the small parts are the last two digits of the serial number. If you find no small parts with a different two digit code then your Luger is all matching, and worth considerably more than one with mismatched numbers.

The S/42 was the Mauser factory wartime production code during the year it was manufactured. Other codes they used include just "42" and "byf"

The different 4 digit serial number on your magazine indicates that it was originally issued with a different pistol by that serial number. It is therefore, non-matching. Matching magazines are very rare.

The digit "1" on the magazine indicates that it was the primary magazine for the pistol it was issued with. The secondary magazine would have a "2" stamped in that location. I am not sure about the "S" with the "SUN" type stamp because I don't have my references at hand, but I think this may have been manufactured by the the Simson company... another Luger manufacturer... someone who knows will correct me if I am wrong.

The gold symbol on the sideplate of your 1838 Luger was added by some owner to personalize it as you have suggested. It does not increase the value of the gun unless there is documented proof that the gun belonged to some famous German soldier or politician. Not very likely. Adding this type of work to a military issued Luger would have been against regulations. It was probably done by the GI who captured the weapon and brought it home.

The P.38 (is not a Luger, but fires the same ammo). It was designed by the Walther factory and was produced by several arsenals. Your photo is not clear enough to see the markings on the slide. The markings should be "P.38" the full serial number including the suffix letter, the maufacturing code: "AC"... this was the wartime code for the Walther factory. If the gun was made by Mauser, it would be "byf" and if assembled at the Spreewerke arsenal, it would be "cyq"

There should also be a two digit number in close proximity to the manufacture code... I can't make it out in your photo, but the two digit number is the year it was made. (41 to 45)