I know the Post is a few years old but That tag actually has 5 Buttons according to the reference Schematic i found, not sure if they are programmed, also includes pinout for the serial programmer. https://wkretype.bdimg.com/retype/zoom/c53d1d2daaea998fcc220ef5?pn=1&o=jpg_6&md5sum=c5c3c60e692d5c4b647440703cd37a03&sign=012a421845&png=0-&jpg=0- The chip also comes in a QFN40 fashion https://wkretype.bdimg.com/retype/zoom/26f4c793680203d8ce2f2428?pn=1&o=jpg_6&md5sum=6743835bee00fb7cd3eb66f3af8014a3&sign=a3f40cc33a&png=0-11381&jpg=0-156245