[Reece]

Yeah, but metal rectifiers didn't catch on much. Some RCA's had all metals except the rectifier was glass. They put a shield around it (no electrical reason to do so) so that you couldn't see the glow and it would "look" metal. I have a 1942 model 28T that uses metals but there is a shield base on the rectifier socket (5Y3) but somebody long ago discarded the useless shield. Metal rectifiers and power output tubes get really hot enough to burn you so fell out of favor. Metals are a great idea for shielding in RF and first audio stages but a lot of people (like me) like to see the glow. Adds to the magic!