Exists in two versions, a 360KB (-001) and 1.2MB (-002) versions. The 360K external floppy can be used with either 5.25" diskette adapters. The 1.2MB external floppy drive is limited to the 1.2MB version of the 5.25" external floppy adapter

Tony sez:
   The 1.2M drive needs a different controller than the 360K.  The 360K will work with the "bay sled" and minimal controller (and appear as the B: drive without any drivers being loaded), the 1.2M needed the more  complex controller (lots of chips) and needed a driver loaded (and would
 appear as E:)
John Johnson (in hiding in Texas)
   There are two different 5.25" external floppy drive setups (drives _and_
 adapter cards) for the PS/2: one for the 4869-001 360K drive and one for
 the 4869-002 1.2MB drive.
  
4869drve.exe PS/2 5.25" Disk Adapter/Option Driver Diskette
525drive.com 5.25" 1.2MB Opt/device Driver Diskette 
 

       The Personal System/2 5-25-inch External Diskette Drive (4869-002) enhances the Personal System/2 product line by making available an external 1.2Mb diskette drive that uses 5.25-inch media. It provides a method for users to transfer data files and execute programs that follow DOS and BIOS procedures from 5.25-inch media when attached to the 3.5-inch diskette equipped systems.
       Unlike the current Personal System/2 5.25-inch External Diskette Drive (4869-001), the external diskette drive (4869-002) and the internal diskette drive (6451006) do not operate as the "B" drive.  This frees up the "B" slot so that it can be used for other features (refer to Product Announcement 188-148, dated September 13, 1988).  When the system is configured for the 5.25-inch diskette drive, the drive is assigned the next available drive letter.  For example, if the using system has diskette drive "A" and fixed disk drive "C", then the 5.25-inch diskette drive will be assigned as the "D" drive.

PREREQUISITES:  Prerequisites are a Personal System/2 5.25-inch Diskette Adapter/A and a 3.5-inch diskette equipped 8550, 8560, 8570, or 8580 system unit with an available I/O slot.

Models
Hi !

 If you turn it around and look at the underside you will find
 4869-0xx, where 
 -001 means a 360K / 110V unit
 -501 means a 360K / 230V unit
 -002 means a 1.2M / 110V unit and
 -502 means a 1.2M / 230V unit