^ that is the underside of this: a Marchant electro-mechanical "figurematic" calculator from the 60s, given to us by @smellsofbikes a while back. we finally got up the desire to do a more thorough assessment to see if we can't get it working again
it has some stuck keys but experience with these things tells us that may be entirely because the motor isn't running. the bottom case has access points in it which are a good indicator of the locations of screws or gears that may sometimes need a little manual assistance, as well as locations where lubrication was applied. and the excess of old grease on the gears indicates maybe it was lubricated instead of fully serviced a few times too many, causing everything to jam up with a lovely dirt-grease combo. so *hopefully* we can get it moving again with just a little careful cleaning and re-lubrication. because taking these things all the way apart is... not fun.
this site has a very thorough description of a similar model: http://www.johnwolff.id.au/calculators/Tech/MarchantDRX/Intro.htm. our other dividing machine, a Friden STW, is less elegant looking but also (comparatively) easier to service - and we still don't like pulling it apart, because it's finicky. there's something like 10,000 individual parts inside. just to do basic 4-function arithmetic.