I agree, one can’t easily tie an NFT to a physical object. Nothing guarantees that the watch and NFT change ownership in tandem.
All I’m saying is that a serial number doesn’t really prove anything because it’s trivial to copy. A private key inextricable from the object would be better, because it could generate timestamped signatures as proof.
Yes. I regret not being more clear in my original comment, because the scheme I alluded to is an application of public key cryptography, such as Certificate Authorities, and is not about cryptocurrencies specifically.
The point of a signed timestamp (and/or challenge string) is that it demonstrates the signature is freshly generated, proof that the device is authentic right then and there. An old copied signature would not have this property.
All I’m saying is that a serial number doesn’t really prove anything because it’s trivial to copy. A private key inextricable from the object would be better, because it could generate timestamped signatures as proof.