Quoted from iceman44:Shoot left ramp to load the ball into the sarcophagus lock. Sarcophagus lowers to flat again, with locked ball immediately behind the captive ball.
Hitting captive ball now will cause the locked ball to roll back to the end of the sarcophagus trough and hit the switch, which registers your hit of the sarcophagus (grants a mummy letter).
Can anyone confirm, mine doesn't seem to empty the sarcophagus when game ends. I typically have to start anew game and wait for a ball search to clear it out.