In days past, if you’ve ever experienced an overheated selenium rectifier, you will never forget the unique smell. In this restoration, they all were okay, so I remounted them in the chassis. I replaced the dissected unit with a modern silicon diode.
I don't think I would've put those back. The only good thing about the toxic SeO2 vapor they release when they overheat is that it smells so awful that you will probably be in no danger of absorbing a toxic dose. [1]
It'd be better to replace them with a 1N400x-diode of the appropriate voltage rating, perhaps with a small series resistor to account for the lower voltage drop in the new part.