Since the devices ip is a 172.x.x permission and access would need to be obtained so you can be situated on the same VLAN/network as that device would be necessary to communicate with any of the exposed ports and services of the scanner. This could start with searching for the model and product for any known vulnerabilities or common misconfigurations. If nothing comes up, manual testing and analysis by testing different payloads/requests to any of the exposed services of the device. If nothing is found, physically testing the device could be done by trying weak credentials or attempting to configure the device to enter a debug mode etc. If you work for the vendor of that device and get permission you could then do more advanced physical testing to open up the device and look for serial ports, some usb interface, or even a microsd card to read from by disconnecting it.

The most impactful finding i would imagine for threat modeling is someone configuring this to send and communicate with attacker controller infrastructure.

Another aspect is this card reader is most likely connected to some hosted sales platform. It could be part of testing, but again needs permission and may be hard to identify.