This read-only string reports the International Mobile Equipment Identifier (IMEI), the unique code identifying the physical mobile equipment (the modem hardware itself) to the network. An admin uses this hardware identifier, distinct from the subscriber-tied IMSI, when reporting a specific device to a carrier for activation, blacklisting, or hardware-level support. For example, if a modem is reported lost or stolen, the admin would provide this IMEI to the carrier so the device itself can be blocked on the network regardless of which SIM is inserted.