That's exactly what it is. Here's a vid where the ball is trapped (note - this was an early software test).
So does Nuggy get a very cool toy award or was something like that done before?
Mousin' Around! has similar ball locks - called ball eaters - on the left and right loops which are activated by completing the MOUSE TRAP stand-ups (helped by the light letter rollovers in the flipper returns). Completing both ball locks enables three ball multiball. Jackpot is achieved by completing the ball locks again (which release the ball this time and drops the ball lock back level with the playfield) and then shooting the right ramp well enough to get to the mouse hole.
I haven't seen a Secret Service which was manufactured a year before MA, I believe, but it looks like it too has two ball eaters which lead to a 2 or 3 ball multiball depending on which targets you hit. Well, I'm sort of guessing as I can't really tell from the pictures.
