I wanted a definite answer on this, so I began searching further to try to find the original source of the BaneBot RS775-18 motors. While I don't have access to a BaneBot motor to peel the sticker off of, I did find this clear image of the 775 motors:
http://www.chiefdelphi.com/media/photos/36263
In the full-resolution version of the photo, two things are obvious: The last four numbers on the first line are "8514" and the last two letters on the second line end in "CW". On the Mabuchi website, they do sell a "775WC" motor with the part number "
8514". These published specs at 18V match the
published specs (for 18V operation) on BaneBots' website. The likely reason behind the letters printed on the BaneBot motors being in the wrong order are due to the fact that Manuchi is a Japanese company, and the BB motors were all made in China (possibly by a clone manufacturer).
So the Mabuchi specs list the power of the Mabuchi 8514 at peak efficiency as 273 W. The BaneBot spec sheet for their RS775-18 at 12V lists power at peak efficiency as 119.25 W. If they are the same motor, then 273W * (4/9) = 121.33 W would yield the expected power output at 12V. The expected and actual power values are only 1.7% off; if BB published their RS775-18 at 12V spec sheet from dynamometer testing, this 1.7% likely could have been due entirely to manufacturing tolerances of the 775 motors.
Thus, unless someone has dynamometer data to prove otherwise,
these specs for the RS775 are accurate.