Hey, thanks for the message and sorry for the delay, I had been working on a few things these past few days.

So regarding blank NFC rings, yeah of course I know what you mean, but the rings you're looking at most usually come with what are called NFC Tags (https://www.nxp.com/products/wireless-connectivity/nfc-hf/ntag-for-tags-and-labels:NTAG-TAGS-AND-LABELS) which is essentially NFC chips, but very low-power / low storage type of Chips (think up to 16kB total storage maximum). We use NXP P71D321 (https://www.nxp.com/products/security-and-authentication/security-controllers/smartmx3-p71d321-secure-and-flexible-microcontroller:SMARTMX3-P71D321) which is a microcontroller with a lot of security elements and NFC functionality. It is the same chip used in bank cards, and it runs JCOP on it; JCOP is an operating system for security sensitive systems and runs on smartcards. Furthermore to put it in a ring you have to get the FPC version of it etc; anyway what I'm trying to say is the options you see on Alibaba aren't really similar to this, to give a more good comparison, the Ace Cards (where you store Shamir) have MIFARE chips, or basically one of the best chips you can get on one of these rings from Alibaba; but we only use the cards to store a seed, so those are basically just toys used to store small amount of information and/or do simple access control (like a hotel key access card).

P71 is also one of the best options out there in terms of security and performance (that small chip has up to 344kB of Flash and 12kB of RAM which I know sounds little but it's actually a lot for a chip of this type). It was also necessary for what we're doing because JCOP alone would have occupied more than the largest NTAG offers in storage (16kB), and that's not even taking security into consideration. Just to give a simple example, if someone were to try to send unauthorized instructions to the chip repeatedly, the chip automatically bricks to protect itself etc.

Anyway, let me answer the open-source questions and everything else. First of all, I want to make clear that the code will be open-source. It is not yet open-source and I'm willing to take that criticism so let me explain why. The reason is simple, I want to publish it with a similar license to Uniswap V3; i.e. if you want to use the code for commercial purpose you will have to wait 2-3 years from every release. And free to use for anything personal. So because of that I am in discussions with lawyers to well, basically, make a license for us. In the best case scenario, the code will be made open-source before we ship the first rings, in a worst worst type of scenario it will be open source within 12 months of right now (taking into account that first rings will be shipped sometime in 4 months from now give or take).

Now to answer the other questions. The Shamir implementation we will be using is SLIP-0039, which is industry-standard, open-source and developed by Satoshi Labs (mother company of Trezor) - https://github.com/satoshilabs/slips/blob/master/slip-0039.md

The difference, here, being, the seeds themselves are actually stored on the Ace Cards as opposed to on a piece of paper, so to the question "will you be able to recover it on Trezor etc" that mostly depends on if they will accept restoring from an NFC card, maybe not on day one, but eventually I think they will. The other question is if they are compatible with SLIP-0039; Trezor I know for a fact is, the others I don't know.

I hope that answers the question but I'm happy to clarify if anything is unclear