[cctalk] What was this AT&T SCSI enclosure for?

I have an AT&T branded SCSI enclosure. Two half-height bays with the drives held vertically (on their sides), with a door that opens to expose one for a tape drive, activity lights labeled hard drive and tape, CN50 connectors, the AT&T beige and brown color scheme I associate with 3B's and 6300 PCs. No model number. Anyone have any idea what this was made for?