Here are a couple of shots of my Power Computing XL drive, so you can all see the difference.
As you can see the drive looks very different to the one Stu has (and the one in the advert).
My drive pictured here was produced after the original plastic one and has a completely plain metal case, and you can also see that it also doesn't have the two switches on the back..
The original plastic one looks identical to my Power Computing 880B Floppy Drive, including the two switches on the back that are for selecting the built in X-Copy Cyclone compatible disk copying hardware. This was one reason I didn't think it was an XL drive as I don't think they have this copying hardware in them, just the 880B 880K models did.