It definitely looks like a Power Computing External floppy drive. The actual model of drive might be harder to work out though. To use the HD functionality of one of the Power XL drives I think you need to have the drivers installed and booting as part of the Workbench startup sequence. Anyone, please correct me if I'm wrong.
You said the drive came with the XL floppy disks. If needed the instructions and drivers should be on there. I think, but could also be wrong, that this will only work on a Workbench 3 or newer machine, such as an A1200.