You're contradicting yourself perfectly. It doesn't matter how simple the firmware is, it's proprietary, and that means users cannot verify your claims without spending the BTC from these notes.
Tangem notes don't need "independent certification" or "manufacturer attestation" if there's no need to trust anyone. That literally means customers are being invited to trust your attestations and certifications.
A significant part of what makes Bitcoin valuable is that anyone can verify the validity of a payment, not just a company paid by a manufacturer to do so. The previous physical Bitcoin producers (or at least Casascius anyway) were very upfront that trust was essential to their product, that made it easier to trust them. The fact that you at Tangem either don't understand that, or are wilfully misrepresenting the fact, makes it much much more difficult to trust you or your notes.
You're drawing your perceived contradictions from using the word «trust» with materially different connotations for a rhetorical effect. Compare:
1. I informedly trust this airplane not to crash, because: authorities are certifying it, Boeing is a serious business, engineers are not murderers, there are many failsafes, planes rarely crash.
2. I blindly trust this stranger to hit an apple on my head with a gun from 30 feet, because: they say they can, how hard can it be, why would anyone want to shoot me, it's so cool.
Tangem was carefully designed and built into #1, Casascius, in any engineer's eyes, is #2.
Our goal is to structure the product in a way where we can't do anything harmful, out of malice or stupidity, even if we really wanted to — including the edge cases of a sudden dissolution of the company or even hostile takeover. Every product will still function forever, and be secure for its lifetime.
To this end, we already closed the trust loop — by keeping the product simple (relatively tiny attack surface) and bridging multinational certifications with independent audit of unquestionable integrity on top of a simple open protocol and reference implementations.
In the consumer space, there's no hardware product that even claims this level of security, much less achieves it.
