Well, i don't know if an official 5,25"-drive existed here. The pricelist offers a complete drive with built-in power adapter, the invoice of the pre-owner of my system also shows that he bought such a kit. Unfortunally the drive wasn't included within my system, but a manual of the BASF 6106/6108 disk drive. I think that Enterprise sent him this drive together with the EXDOS-interface and maybe also a case. So the document about the steprate problem should be for the BASF 6106/6108 drive.
Edit: Ah, i see that the pricelist says "180kb". So the drive should be the single-sided BASF 6106