Never saw such a bell transformer around here. Even the oldest one are in a nice black bakelite enclosure with shrouded terminals. Modern ones are designed to fit a DIN-rail panel.

I think if something like the old stuff on the wood were mounted like that there would be a sheet of asbestos between the wood and the electrical stuff.
We had some light switches that were screwed to the wooden door casings and they had a hand-made asbestos backing. Carefully removed it... [Linked Image]