I found a Mallory 1B8R here: https://www.antiqueradios.com/...hp?f=15&t=336750.
The ad below the picture of the rectifier makes it appear that model numbers starting with 1B8 have eight junctions (says the 1B8R has 8 junctions instead of 4 like the 1B4R above). I am wondering about the eight junctions.