Thanks for the info. There's a manual out there for the 500 series, too. Either mine is missing the take-up spool or it's a deeper mystery. I still wonder: in some of the pictures you provided, you can see the gear on the take-up spool (which on my camera is attached to and operates the film counter dial on the top of the camera, and on yours as well, presumably.) Mine has no take-up spool and no gearing evident, yet the film counter still works properly. This tells me that the gearing to operate it is different than in the examples you show, but it's still a mystery to me.
Oh, well: I should join the rangefinder website, I suppose, and see if anyone there knows anything about this. Thanks for your help: I appreciate it.