What a coincidence, I've just finished cleaning out and checking my second 6632B.
The first one I got from a seller in Finland had a visibly faded display but was otherwise in excellent condition, this one looks even better externally although I noticed some corrosion on the metal inside. Not sure what kind of dust this thing has been inhaling, so I took it apart completely and washed the boards off to be on the safe side.
I've also been playing around with these, GPIB and a Keithley 2015. I stepped through the entire range in 10mV steps and logged the voltage measurements of the supplies and the DMM, and both my 6632B's matched the Keithley within 0.01% over the whole range except at the very low end below half a volt or so.