Wow! Very nice 6239. The 1.0mil serial would put it around 1963. The watch would have been equipped with a Valjoux 72 when it was made, and these movements/different variations of it where used until around 1988 when a new model came out, the 16520 featuring the automatic winding caliber 4030 Zenith movement. Once restored this is about a $23-$25,000 watch assuming that spot near two o'clock is just a spot on the acrylic crystal and not the dial.
As far as restoration goes there are several good options, Rolex USA NYC not being one of them as they do not like working on vintage pieces. I would contact Bob Ridley/Watchmakers International as said above or ABC Watchwerks here is Los Angeles. Other members should chime in soon with other suggestions for watchmakers.
