Could be just the Serial Numbers, but you can always ask. A few crazy collectors get all worked up over Serial Numbers. If it is one of the very last of a run of a famous camera, the speculation is that it will be worth more in the future. The last 100 or so Leica M6 cameras are sure to fetch a premium.
Myself, I only get crazy over Nikon Serial Numbers. Leica's are just too nice all-the-way around to fret over such details; Canons are also great for putting film through; no one seems to care about Retina SN's, just whether it has Ektar or Tessar lenses; Contax: Color Dial; yup only Nikon collectors would pay a premium because a camera can't be used with a flash...