This deprecated object reported the device ID of the neighboring SummitVC stacking unit connected to a given Summitlink stacking port. Since it's deprecated, an admin should be aware this was used on legacy Extreme Summit stacking hardware to identify which stack member sat on the other end of a given stacking link, and shouldn't expect current platforms to populate it meaningfully. A value of 3 here would have indicated that stack unit 3 was the neighbor connected via that particular Summitlink port.