There's something of a convention among some Japanese motorcycle manufacturers where they refer to their products as the model plus a chassis version plus the year of production.
There are three ST models: ST1300, ST1300A and ST1300PA. You'll find this in the lower-left corner of the VIN decal. Most of the decals have the product code and process revision (MCS-G00 or something like it, same scheme you find on parts) in small print underneath.
There is one version of the chassis, A. (Some other bikes, like the XR250 has an A and B version).
For the year, Honda appears to be using the same
ISO year encoding used in VINs. (Others use a sequential number; the Kawasaki Vulcan 750 was the VN750A1 through VN750A21.) On Hondas, the four-digit model year is printed on the VIN decal in large type at the bottom.
Honda doesn't seem to use this scheme much in North America; usually it's just the year and model (2004 ST1300A). It may be more prevalent elsewhere if governments require a unique name for each year. The UK further confuses things by encoding the age to within six months into the number on the license plate, so you'll often hear people there refer to having a "
xx plate" where
xx is a two-digit number.
--Mark