I just tried googling those key words "12x10, sovereign, kellyco" and can't find any links on Kellyco that show the Sovereign version. And, I just did a search on kellyco for "12x10 sovereign" and those links have nothing either. Maybe they aren't going to carry the Sovereign version anymore, but again that doesn't mean Detech isn't making it. Check FleaBay or Joann Detectors in the UK, but first I'd wait to hear from JW. I'm going to shoot him a PM and see if Kellyco isn't carrying the Sovereign version anymore, as well as ask him if they still plan to carry the 13" Ultimate Sovereign version, because a month or so back he said they were going to carry the Sovereign version of that coil...but did say they'd have it by mid-May.
Just googled 13" Ultimate, Sovereign and I see the guy still sells that new on Fleabay. Oh, and by the looks of it the Sovereign version might be black instead of white? But I don't think he ships to the US anymore (heard he did early on), but I bet he would if you asked him to.
Come on now. If Kellyco carries the Ace 250 version of these coils (even the 13" Ultimate for it!) then WHY wouldn't they want to carry the Sovereign version of both coils? The Sovereign has been made for, what...20 years now? Got to be a ton of Sovereigns out there. I know the 12x10 has my GT getting the depth and unmasking just as well as my friend's flagship machine when we compare signals. It's like putting a turbo charger on your Sovereign. I'm just glad I've got mine already if Kellyco isn't going to carry anymore.
You can also put a Want To Buy add here on FIndmall, as that's how I got my GT, 15x12, 12x10, and my S-5. Often by doing that you also get better deals, as some people don't want to post a for sale add, but will PM you about getting rid of something when they see you are a ready buyer. Just click on their name and check out their posting history. If they've been posting on here for years then chances are they can be trusted. In particular, see if they've sold any stuff on Findmall before and see if any feedback is posted in those for sale ads they posted. That's how I knew I could trust the people I bought from, and how they knew they could trust me.