My understanding is that specific watch movement sizes may vary for one manufacturer to another. Example: I have read that a South Bend 12 size watch movement is slightly larger (or smaller) than 12 size watches from other manufacturers. Therefore they won't fit in cases made for other 12 size watches. To my specific issue, I have a very nice hunter style 6 size case. When I got it, it contained a 6 size South Bend watch. The watch is "toast" so I am considering selling the case. I need to know what manufacturers' 6 size movements will fit in it and which (if any) won't fit. Is there a guide somewhere that lists size compatibility of various manufacturers? If so, where can I find it. If not, can someone at least tell me if a case made for a 6 size South Bend will fit other manufacturers movements? FYI, I am aware that a South Bend 6 size is the same as a Columbus.

I don't have an answer for you with regard to your 6 size case, but I have had difficulty fitting 12 size Hamilton or Illinois movements into anything other than a Hamilton or Illinois case (seems like it's a 12 size thing, not much of a problem for other sizes). Elgin or Waltham movements seem to be a fit for most American made pocket watch cases.

Barry