Used, tested, Celan Technology EMacIIC Nubus Network Card for Macintosh with 10baseT(UTP), 10base2 (Thin Coax/BNC) and AUI ports. The required interface is set via an on-board jumper; 'A/B' form AUI & BNC, or 'TP' for UTP.
Note that thin ethernet networks require termination with a 50ohm BNC terminator at each end of the chain (unless the last node is an Apple AAUI transceiver which self terminates).
Driver software may be required (not included). It may not be compatible with the Centris/Quadra 660AV but can be used in any other Macintosh with NuBus slots.