Construction and Specifications of H Cat 12B?

I recently acquired an H Cat 12B in nice condition, but with no owners manual or any other significant information regarding its use and design.

Does anyone have any information on constructions specifics of this pre-amp? Any idea of what its input and output impedance's are, or output voltage? Is there a recommended protocol for setting up the Wavefront dial? Any idea what the output devices are? I suspect FET of some sort, but not really sure. Just whatever information you can provide would be greatly appreciated, as I am just trying to get acquainted to what this pre amp is capable of. So far I have used it in front of an Electra Print 300B Custom amp, and a N.E.W. DCA 33. The results are encouraging, but I would just like to know a bit more about what I bought....