They do keep excellent time.
Mine makes no noise (well I cant hear it, put it that way)
I don't think anyone has opened them up on BB.....I suppose if you removed the 2 bulbs at the back and those tiny nuts you might be able to pry off the circuit board and get inside there to have a look
but then again you might just break it....and they are very expensive when you do find a used one (or NOS) somewhere...
seller in Germany has a used for 150 and a NOS for 300 euros!