A question: in the "early" regulators/rectifiers there are 2 round, metal electronic components pushed into the back of the metal box.
On this picture you can see them on the very rhs of the metal box.

This way they get sufficient cooling. In the past I found out these 2 components are PS620 (0.5 Amp). Searching the internet I did not find any reference. Does anybody know if these components are still available? What are they? Transistors, thyristors, something else? If no longer available, what would be a similar, replacement item?