CC, that's a 20SC enclosure. It's the SCSI ZFP drive Apple released shortly after the Plus and has a different enclosure than the HD20 (which used the floppy port). They made this series in a bunch of different capacities. My 20SC has an 80MB drive inside, which I believe was actually pulled from a IIx, as it's the only other model where I've seen/heard the exact same 80MB Apple-branded 5.25" drive. I do have the original box for that drive enclosure.

I don't have the box for the CD 300e, but that's exactly what the smaller drive is. I do have a 150e with the box though!