experience tells me that sometimes a "leftover" bike can be registered under a later year. Anyone have the pre-2000 year codes? Thanks!
That really doesn't happen in The USA since the 17 digit VIN was fully adopted 30 years ago.
The tenth digit tells you what the production model year is on any vehicle, and that is consistent worldwide, now.
They run through numbers 1-9, then go to letters. The letters U and Z and the digit 0 are not used for the model year code.
Further info, if you want it:
1st - 3rd digits - ZGU = Italy, Moto Guzzi
4th - 8th digits - KD0KD (or whatever) = model information
9th digit is a mathematical check digit
10th digit is the year model. In your case, "X" being 1999.
11th digit is the plant code. On Guzzi "M" is for Mandello del Lario.
12th - 17th digits are the production sequence.