This picture shows Q (Scott Lumsden) testing the Rev 1 Ridgewing bridge pre-amp which he designed, with the bridge cover removed. The black tone & volume knobs are visible along the bottom edge. The rechargeable lithium ion battery is the silver circle at the upper right edge.  The small rectangular feature between the T/V knobs and the battery is a little “buddy board” stacked on the circuit board’s vertical bus. This particular buddy board has a bunch of indicator LEDs. The vertical bus is an open invitation to add buddy boards bringing arbitrary electronic functionality to the bridge. It is pretty straightforward to make taller bridge covers to accommodate multi-level boards.

The screws for attaching the cover also hold the circuit board in place, so without the cover the circuit board has nothing to hold it but the pickup lead from the under-saddle piezo which is why it appears a bit cockeyed.