Hey @jhlewis sorry for the delay in responding… very busy these days…
Anyway, the mifare ecosystem is very confusing yes! I don’t even want to get into it… but basically “Mifare S50” was a 1k chip that is now called “Mifare Classic” … it had 4 ID bytes which used to be called UID (unique id) but it’s only 4 bytes… so now they have lapped themselves a couple times and re-used the same IDs over and over, it’s called NUID (non-unique id)… but the S50 also had a security flaw in it’s crypto1 algorithm used to protect keys, so they re-released “mifare classic ev1” … ev1 = evolution1 … i.e. the new “classic” chip is byte for byte compatible with the original “classic” chips but they fixed their algo…
In short, the xNT uses an NTAG216 chip which looks very similar in memory structure to the older Ultralight C chip, which is not “mifare classic” compatible, and has a 7 byte UID (probably soon to be called NUID but I digress)… so on the surface it does not appear to be compatible… however… both chips use ISO14443A to communicate, and some systems don’t specifically use the memory features of the S50 classic chip, they just care about the ID… so in that case you might be able to supply the first 4 or last 4 bytes of the xNT UID to the system and it may work… or if the systems supports it, all 7 bytes.
We do have a very limited run on right now of the xM1+ which is an S50 1k emulator chip… but it comes with heavy technical risk. Read the post carefully.