This read-only 10-byte DisplayString gives the hardware revision of the complete assembled ComPort unit, as distinct from just its internal board. It matters when a hardware change spans more than the main board (enclosure, connectors, etc.), so support can classify a whole unit's generation rather than only its board. For example, a field advisory affecting a particular unit revision (but not necessarily every board inside it) would be checked against stuUnitRevision when deciding which deployed STUs to replace.