[ithacaartist]

Correct; it's part of the serial number; yours, therefore, is 3288m. Include this full number in all related paperwork for your Luger!
Barrels are typically serial numbered, along with many of the small parts. I think there is a list in the FAQs of what whould be numbered, and how--(commercials differ from military).
The 8.82 is the measured I.D. in mm of the bore, between lands of the rifling, and this number, or one close (by a .01 mm or so), is most often found on a 9 mm pistol. There is another system of indication of this dimension used on early pistols. Someone else may explain what the other numbers are based on, and when the feature was changed from that early style to the type of numbers you're seeing on yours.