IIRC, first, that's NOT NuBus, it's an SE PDS PassThrough adapter whose EuroDIN connector is easily mistaken for NuBus by eBay 68k Noobs (to put it mildly). Its function is to allow an FPD or TPD Display Card to be used along with the Radius 16 or Radius 25 Accelerators in the aforementioned SE . . .
. . . or not! :-/