|Janice Piette Venture-Agent, Ohio—Columbus aka Cirithiel|
So, jewelry did not exist until Ultimate Equipment was published?
No, prior to that it was listed as 'Treasue.' The one itemized jewelry, signet ring, is listed as Adventuring Gear.
UE listing jewelry under Clothing rather than spending the print space to create another heading does not make jewelry clothing anymore than listing a stirge and pseudodragob under Animal makes it an animal rather than a magical beadt or a pseudodragon an animal rather than a dragon.
By a strict reading of the rules, I still think the only jewelry available for PFS characters to purchase are those I listed above from the Core Rulebook or Ultimate Equipment, both under the category of Clothing. (I do not own every Paizo book to check, but these are the only two sources I found when I searched.)
Treasure is not an item a PC has ever allowed to purchase and keep.
As you note, Signet Rings are Adventuring Gear — they are practical items with a specific purpose. In the examples I’ve seen, they are generally plain items, not decorative ones. They imprint a symbol into the sealing wax of a letter. It is no more “jewelry” than a pocket watch would be.
If I were really in Rules Lawyer mode, I might point out that Striges and Pseudodragons are in table 2-3 “Pets and Familiars”, as well as table 2-4 “Hunting and Guard Animals”, so they count as both animals and pets.