What you see here is a MiFare Classic keychain fob that is blank and could be used and found in either electronic locks or customer identification or other systems where a small and easy to carry tag is desired. But in general, this product has an antenna, a NXP S50 chip, and is powered mainly in a passive way whenever it gets placed few inches away by the reader/writer.
Besides that, although reading can be successfully done by any 13.56MHz RFID/NFC reader, you should still make sure if it handles MiFare cards since it supports some other encoding standards.
However, good news is that it has been tested with PN532 NFC/RFID breakout board and Adafruit NFC/RFID Shield for Arduino, and it works just fine with those.
Not only they can be stored and written to 1KB of data divided into banks and found into writable EEPROM, but also, they are able to handle re-writes reaching more than 100,000.
In order to read and write data to the EEPROM inside the tag, check this out:
PN532 NFC/RFID breakout board or Adafruit NFC/RFID Shield for Arduino
Also, we’ve already put permanent 4-byte ID into the chip to help you in identifying one tag from the other. (ID# can’t be changed)
S50 chip specification: