I only see the Quebecois Dr. Jacques Ferron mentioned here once, as a possible father to Jock, so I don't know if this has been discussed before (sorry if it has). However, Ferron reportedly had nine children by two wives (between 1945ish to 1955ish) and I can't find a single one of his children mentioned by name anywhere online. Jock allegedly stated that his father disowned him, and Ferron was a highly respected physician and medical researcher in Quebec at the time. It wouldn't surprise me if Ferron, for whatever reason, disowned one of his children. Additionally, the names Jacques, Pierre, Johan, Jean and Jean Paul seem to be very common in the Ferron family tree. Nothing unusual, sure, most of those are very common in francophone families, but I still think it's worth mentioning.
Also, was the ring ever checked for a maker's mark? Since it isn't mentioned anywhere I lean towards thinking that it didn't have any markings besides the initials. If that's the case, it has to be extremely unusual, doesn't it? Unless Jock got the ring custom made by a small and independent maker, there wouldn't be any reason for there not to be a maker's mark? Sure, it could've been filed off at some point, but why? The ring also could've been older than Jock himself, but the florentine finish wasn't really a thing before the late sixties. If there was a maker's mark, the investigators should have been able to trace it back to the shop where it was bought, or at least to whom the ring was distributed for sale. After all, it's not like it was a very common ring, even by 70's standards!
Sorry if this has been discussed before, but I can't find anything about it.