This read-only integer, ranging from 0 to 255, reports a combined identifier-and-revision code for the network element's backplane, encoding both the backplane's hardware ID and its revision level in a single value. Admins and support staff use it as a compact way to identify exactly which backplane hardware and revision the chassis has, useful for compatibility checks or when reporting a hardware issue. For instance (illustrative), a nncExtPositionBackplaneIdAndRev value of 20 might decode to a specific backplane model at a specific revision, information a support engineer could use to confirm compatibility for a card upgrade.