Monroe electromechanical calculators

I brought one of these home from Bletchley last weekend - turns out they're quite addictive little things :-) It's a Monromatic 8N-3-213 which was marked as broken - I thought I'd see if there was anything obviously wrong inside, plus of course I was curious as to what the innards of such a machine looked like. Question - does anyone have service information for these machines (yeah, right!) or useful tips on things to check over? So far I've found an acorn jamming up the works (!!) and lots of dirt, but the mechanism's reasonably oily still and in good condition. Some of the keys seem to jam occasionally or not latch - I'm hoping that's down to dirt rather than wear (it seems to be improving the more I tap away at things to be honest). After checking that everything was free to turn without jamming I applied power... There's some earth leakage which would be useful to track down - possibly a break-down in cable insulation? I've not worked out what the large rotating thingy on the outside end of the motor shaft does yet though, as this seems to be connected to an insulated plate (and throws off quite a few sparks when running) Can't say I've ever seen such a complicated thing. Electronic circuits don't even come close in complexity :-) I don't think I'd be up for a complete stripdown and rebuild; I'd never get it all back together. ps. Is there a better place to ask than here? Not sure whether electromechanical calculators are on topic or not! pps. Anyone care to guess a date for this machine? I'd make a wild guess at mid-50's but really don't know. cheers Jules