Looking for any info on a Tensor AC-DC Ref Source

[tobe930]

Hello

Spring cleaning and want to fix up this project that has just sitting because I can't find any info

I am looking for schematics and/or manual ok ANY info about
 
Tensor Electric Development Co, Inc.
AC-DC Reference Source
Model 5890

ok I know it is likely to be a great 0.01% reference .. but it is a piece of history that I would like to get back working

Thanks for reading this and/or any info or leads you might have on it.

Tim