Bonus-7 is the sister game to Super-7.  You have your standard (at this point) Mystic Lines gameplay, but now, the extra game is called Bonus-7 and has similar rules to Super-7.  Bonus-7 requires you to make a number combination with your first two balls that equal 7.
Next, you have to get a red outlined hole, then yellow, then red.
This machine also includes a sunburst feature that will automatically award you maximum odds on the Bonus-7 game on your next game!
 
Backglass:

Cabinet:

Playfield:
http://bingo.cdyn.com/machines/bally/bonus_7/resources/pf-bonus_7-1.jpg