Thanks for this info - it got me started...

... BUT:

The drive is mounted in a portable case with a power supply. It has a 50-way D connector on the back: this feeds onto a PCB under the drive, which is obviously a controller for the drive unit, to which it is connected by another 50D. I can't see any jumpers/terminator packs that would hint at SCSI, on either the PCB or on the drive itself.

It is labelled as a CP150B - does that make a difference?