I think it's all to do with destination markets. In Europe for example the tank stickers come in different languages and are on a sheet so you can put on the applicable ones (given the choice I wouldn't stick on any!)
VZR1800 is on my owners manual and the bike is badged M109. Essentially 1800cc's is 109 cu.in's so it's all the same but different designations for different countries.
Boulevard (Line) M109R (N. American Model) VZR1800 (Official Model) My best guess. My ZX-10R was a ZX1000C, and my ZRX-1200 was a ZR1200A I think. The official model is what they use on the microfiche and title.