[Amps] diode info sought

[gdaught6 at stanford.edu]

Hi All,

I've acquired some Solitron rectifiers as follows:

Big black "hockey pucks" about 3.5" in diameter, on a 4" metal disk.  
A big bolt protruding from the black material is one connection, and 
the metal disk is tapped for the same size bolt.

Text on black package reads

Jan  M19500/404-03
7020          CDCD
SOLITRON DEVICES
MADE IN U.S.A.

Can anyone tell me what I've got?  (The Solitron website and Google 
don't help.)

73,

George T. Daughters, K6GT