Most manufactures of non titled equipment have gotten away from model years and now just bring out improvements as they update the equipment and so note the changes as different part numbers from a paticular serial number range and so on.
That may change a little as the emmission standards tighten, as the EPA goes off of years so a paticular year "engine" has to meet certain standards.
How that might apply to a actual year of tractor is unknown. They may adopt a date manufactured to meet certain emmision standards, but not a formal model year like the automotive manufactures do.
In other words say a BX25 tractor produced 3/2013 is not a model year 2013 persay, but only for the eyes of the law does it meet year 2013 emmission and safety standards. Still, it is sold as simply a a BX25, all BX25's technicaly the same without years. But possibly with detail differences in manufacture. When the actual model changes due to a major design change, then that is indicated in a new model number (sorta like the progression of BX 23, BX 24 and BX 25, no real model years, but real design changes)
Food for thought
David
EDIT - Yamaha outboard motors (non titled) has done this since 2006. There are NO model years since then. A good example might be the 225hp four stroke outboard. While no model years, there are serveral detail parts changes and updates that require a serial number to get the correct part - They do however have a built on date, but that is only when the outboard was built, and has absolutly no corrolation to any model year in the normal sense. You will also see other decals noting that the engines meet a paticular years emmission standards, but then again, that has no corrolation to the model year, just that years emmissions standards.
MerCruiser has done this for 40+ years, no specific model years, but serial number ranges for paticular models and changes during there production run
