Hello Charlie, I hope you're doing well,
Every router in your thread network has a unique identifier called a PAN ID, maybe this can be of use to you so you can distinguish each device.
To get this value, you can use the srcPanId value in the MAC_STRUCT inside the MacInterface.h library.
This value can also be obtained through the use of a serial terminal, by inputting the "panid" command.
Best regards,
Sebastian