Found it!
I have a couple of these modules...
http://www.vintagecalculators.com/html/novus_650__mathbox_.html
... right down to the 470 Ohm resistor
And a couple similar ones with 8 digits which might be the main
component mentioned in the text of the above page as the "model 852"
(especially since my LEDs are marked M850!)
... or maybe it's this...
http://www.vintage-technology.info/pages/calculators/n/novus850.htm
Thanks for the nudge to Commodore, Will... that gave me a good
starting point to end up at the Novus series.
Now to power them up and stick a keypad on them.
-ethan