No, it's not a version number. Sire's naming scheme is simple:
The letter pretty much tells the body style, whereas the number tells the "range", with a higher number means something "more expensive" aka more / better features.
An added R means rosewood fretboard, an added P means passive (only if the base model is active).
D5: vintage Precision bass with single coil, passive
M2-7: "modern" body with humbuckers, all active
P5-10: Precision bass body, P5/P5R passive with P-style neck, P7-10dx all active with PJ pickups and J-style neck
U5: short neck PJ passive
V3-10: Jazz bass body and neck, V3P and V5/V5R passive, all other active
and if you add a couple of zeros to the number, thats your price range.