Could be someone mis-stamped the tag, I've seen that before. I've only ever seen the two 2wd codes, 657 and 658. 2050 and 2150s used the same 2wd transmission.

Most of the transmission parts were used in other models, so you shouldn't have too much trouble there. The ring and pinion does show a serial number break on the 2wd. Both were 9 teeth pinions, so I'm not sure what the difference was, but there must be one. I haven't found another model that used that pinion, so that's going to be the toughest part.