<>It's a TK50 in an external case with a single 50 pin D-sub connector and <>no ID switch. < < A single connector? A D-sub 50 no less? < < Geez... that's downright psychotic. Ok, I'm baffled. Anyone else? Sounds like a externally mounted TK50 for use with the usual Qbus M7546. The companion was the externally mounted RD5x for use with the RQDXn and the matching distribution card. Both are for those that had BA23s and no place left for a disk or tape. Allison