[judge2020]

This front page seems to include a lot of info - it had a ‘Sub-1 GHz Transceiver’, then it has ‘125kHz RFID’:

> Low-frequency proximity cardsThis type of card is widely used in old access control systems around the world. It's pretty dumb, stores only an N-byte ID and has no authentication mechanism, allowing it to be read, cloned and emulated by anyone. A 125 kHz antenna is located on the bottom of Flipper — it can read EM-4100 and HID Prox cards, save them to memory to emulate later.

And

> Flipper Zero has a built-in NFC module (13.56 MHz). Along with the 125kHz module, it turns Flipper into an ultimate RFID device operating in both Low Frequency (LF) and High Frequency (HF) ranges. The NFC module supports all the major standards, such as NXP Mifare.