VHF radio
I just went & looked at that panel... it is screwed and glued in place: not to be taken off. You can reach the rear of the radio through the opened electrical distribution panel: you can't see it but you can touch it. The Raymarine 218 is held in place by two L shaped aluminium extrusions: one leg is screwed into the radio itself and the other has a bolt which when screwed in exerts pressure from the back on the panel.
1- You unscrew these two bolts to relieve the pressure.
2- Yoiu then unscrew the bolts that go into the radio: these have a large plastic knob.
3- Once these are removed along with the L-shaped pieces you can remove the radio.
4- You then go the bottom of the compartment below the radio and retrieve whatever you dropped!
If the radio is defective you can reolace it with a Raytheon 55 and the bezel they sell. This radio is front-mounted but you will have to glue a support for it and use some wood backing to screw the new radio in. The Raytheon costs half the price of the 218 and communicates with the remote microphone unit. It doesn't have a hailer or siren attachement.
Have fun, this is a bit of a chore.
Pierre