What is this strange component from 1950 radio reciever
That's a selenium rectifier.   Google "selenium rectifier" and there's loads of info, photos.   They've been obsolete since the 1970s.  Decades ago, they were cheaper than vacuum tube diodes, and semiconductor diodes couldn't handle higher voltages and currents.  The parallel plates are indeed for cooling.

http://en.wikipedia.org/wiki/Selenium_rectifier