[ARC5] Question: What is a BC-688-A?

[jcoward5452 at aol.com]

Thanks everyone,in advance.
  I just have the housing with tags and connectors and the contract date 
indicates 1942.Just would like to know what it was.BTW this will become 
a power supply as it is just an aluminum shell,not even a tube socket 
left in it.So I hope you all don't drag me over the coals if I make 
something useful out of it.I will retain the outward appearance as best 
I can but may have to change the connectors to something more to my 
specs.I won't drill if I can help it!
  Jay KE6PPF