After about three years' time, I can call this one "done". The case looks to be hand made, from maybe the 70s, likely from Vietnam. It's nearly perfect, though a little too rounded on the sides. Inside the case back is the curly Rolex logo from the era, stamped deeply. The serial numbers are age appropriate and it has BREVET+ between the 12:00 lugs. I put a Brevet+ crown on it, and the dial is correctly dished, but chipped around the edges because the case maker didn't provide a good way to anchor the movement inside. The hands it came with were horrible, made from bits of different hands soldered together. The hours hand looked like card stock and the seconds was 2mm short.
Over about a year I put together the parts, including a Tonny Watch negative relief gloss gilt dial (magnificent) and a perfect set of hands I found on eBay. We went back and forth and decided to use the original chipped dial because it has the patina and it's correctly dished. I went with a low beat ETA because a reliable A260 movement doesn't exist. And now here it is, and dang it, sitting here on the desk beside me it looks exactly like my 62 year old gen 6536/1. It looks absolutely genuine. I wish I could upload high quality photos to do it justice.