1. Key.
 2. Jack.
 3. Jack-operating spring.
 4. Cushion limiting rebound of jack.
 5. Button and screw regulating escapement of hammer.
 6. Hammer-butt and operating face.
 7. Hammer-butt pivot.

 8. Hammer-shank.
 9. Hammer-head.
10. Check.
11. Damper-lifter.
12. Damper-head.
13. Action-rails.