4869drve.exe PS/2 5.25" Disk Adapter/Option Driver Diskette
525drive.com 5.25" 1.2MB Opt/device Driver Diskette 

   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

The 4869-xx1 has an embossed "Star" symbol in the faceplate of the drive.

 If you look at the underside you will find 4869-xxx, where 

 -001 means a 360K / 110V unit
 -501 means a 360K / 230V unit
 -002 means a 1.2M / 110V unit
 -502 means a 1.2M / 230V unit
360K ONLY 72X6758  (almost a bare board)
1.2 / 360 Early 15F7996 NEC 72065C
1.2 / 360 Late  15F7996 NEC D765BC

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:)

       The external diskette drive (4869-002) and the internal diskette drive (6451006) do not operate as the "B" drive unlike the current Personal System/2 5.25-inch External Diskette Drive (4869-001),  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.

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