Great disassembly job. There's yet another branch of the rabbit hole that Tom almost fell down:

   ... the multiplier is based on a classic form, 
   having a translinear core, supported by three 
   (X, Y, and Z) linearized voltage-to-current 
   converters, and the load driving output amplifier.  
   I have no clue how the thing works!

The 'translinear' school of design was founded (or at least popularized) by Barrie Gilbert at Analog Devices (https://en.wikipedia.org/wiki/Translinear_circuit , https://en.wikipedia.org/wiki/Barrie_Gilbert ). Gilbert was one of the undisputed GOATs in the analog field and a full-fledged Renaissance man in his own right. It's worth reading more about him if/when you have the time and inclination.