Thought you might appreciate the similarities between your and my Accutron. Just this week I had pulled my 218 N0('70) from storage and whatever came over me-I decided to overhaul it myself.
(note: I am not a watchmaker but have years of experience with vintage and specifically pre-quartz electrics. I can only do a basic service/regulation of movement though and have no skills to disassemble any of the clutch/tuning fork/or gear components) That being said, I was able to regulate it to what now seems like approx +/- 1 sec per day though I am not exactly sure how except for persistence and luck. I was able to repair the back winding stem from slipping by examining it under high-power scope and determining there was oil/crud built up. Again-just dirt, no actual 'break'. The gasket seal was amazingly pliant and supple so I re-used it for better or worse.
I also cleaned out the battery compartment from buildup. I was having intermittent running and thought this may be one thing causing it. Its fine now so I can only assume. I never have been certain why Boluva used plastic battery reducer rings in these as a standard 389 size seems to be what the movement was drilled out for. But the plastic ring also isolates the battery side walls. Hmmm, on this point. Accutrons are already a bit odd with voltage and they have the battery set [+]positve down unlike most other brands (afaik)
**I was never a big Accutron fan back before my days on WUS and in fact-I received an Accutron like yours, a '75 from death of relative and I used it like a beater and it held up faithfully for man-years and then the clutch went and it was kaput. Then, (and this is SO painful to admit still..agh!) I received thru another incredible fluke a solid 18k gold case/gold dial/gold bracelet Accutron Astronaut in the mid 90s. And guess what? I did;t like it. Not its style. Did;t appreciate its GMT function. I just thought it was way too much bling and even spot gold wasn't outrageously high at the time. And like an idiot. -or I should say-like a pre-WUS dummy- I took it to a Jewleler and sold it for a pittance of what it would now be worth. And whats worse-had I kept it-I most certainly would be wearing it and liking it very much. But then I was the guy in the 80s who inherited a '60 GMT an almost sold/trade that for a song too -not 'liking' its blue and red thing.
Now I would pretty much kill for a decent black dialed SS Astronaut for a decent price. I don't have a lot of regret like that but that Astronaut will always remain with me as a lesson in how stupid it can be to sell something without knowing what your selling. It was a reputable Jeweler who I come across years later and 'humorously' mentioned his ripping me off (i guess I'm still 'hot' about this. His attitude was totally: "eh. you win some and lose some" So. he isn't wrong, exactly. but, he definitely saw me coming back then.
Anyway-that is my 'Accutron story and sorry I have no better advice on serve then the others. In fact-my experience has been the few guys who can do repairs are not very polished in other areas of watch finishing. (sloppy) So-I am on my own for now.
I think our dials have the exact same index markers and mine is just a no-date and a back-winder. The quality and finish of this watch rivals most of the best mass produced luxury dials. And lately I have grown much more interested i plain no-date 3-handed watches so my buying this one years ago allowed me to get a decent example for less then $50.