NFC RFID Card CUID Gen1a Magic 13.56MHz MF Classic 1K for Proxmark3

Description

UID-changeable Gen1a Magic RFID/NFC Card for Proxmark3, Flipper, access control, pentesting, etc.
Operates on 13.56 MHz and emulates a classic 1K, 4-byte-UID card popularly associated with a litigious manufacturer that likes to file complaints to eBay for naming their brand.  This chip supports the "Gen1a" Chinese Magic commands, to allow access to block 0 to rewrite the UID and other manufacturer specific data there.  This is a true CUID device, the UID can be changed repeatedly.
!! NOTE !! This CANNOT be UID changed using the popular MCT Android App.  You need to use a Proxmark3 or similar specialized tool.
You can write the user-accessible blocks with MCT or other apps, but cannot change block 0.
Message me if you want a specific UID written before shipment, otherwise you will get a random factory assigned one.  I am generally not going to accommodate more involved custom writing requests, but you can do that yourself with common tools.