Tool for "BLUETOOTH® Smart Radiator Thermostat" model known as "CC-RT-BLE-EQ" form the brand "eQ-3"
https://www.eq-3.de/produkte/eqiva/bluetooth-smart-heizkoerperthermostat.html
This snipped derives the PIN that is shown on the display when pairing the device from the thermostat serial number which is labeled on the bottom of the device under the battery cover.
Note that the Bluetooth connection is any secure and the PIN is just more or less fake. But it might be useful to indentify the device you are pairing to.
GPLv3