[Boatanchors] Part id

[telegrapher at att.net]

I found a box of rectifier assemblies that i'd like to get info on. 
Only markings on them are "GI HVPR10-MX12 8541".  They are a diode in a 
fairly decent block of whatever it is they used to seal them in. 
Measures about 3 in. long, 5/8 in. wide and 5/8 in. high.  2 terminals, 
one at each end for a push on connection.  No other markings.  I' 
suspect they are several KV at the least but don't have any idea as to 
their current rating.  Any ideas.

Larry
W0OGH