This string is the hardware revision identifier of the component underlying this internal backplane link. It matters on the internal Ethernet link that carries a blade's traffic from the chassis I/O Module up to a Fabric Interconnect over the backplane because certain firmware or interoperability issues in UCS are tied to specific hardware revisions, so this field is often checked when matching a fault against a known bug. Cross-referencing a revision value from this backplane link against Cisco's field notices is a step an admin would take before escalating a recurring link flap as a hardware defect.