Yamaha YM4 for U1 variant ?

[gvelim]

I came across a U1 with S/N 599xxxx and code YM4. The dealer mentioned that is a U1 Model, Japanese import, A+ grade.

The look of the this piano is identical to a U10B that was sitting next to it however I got confused as "YM4" has no "U" in it

Is this a genuine U1 offer ?

Much appreciated,


PS: If would be great if someone could point me to a location where all the different "U1" letter combinations are explained as I find it difficult to understand what I am being offered.