As to help clearing sight about VMS / MicroVMS versions:

I've looked into some VMS V4.x tapes and found out the following:

Version Type     Date written   MicroVAX support
V4.0    Full     23-SEP-1984    NO
V4.1    Update   11-JAN-1985    YES VMS041.A-VMS041 / VMS041.B-VMSONLY / VMS041.C-UVMSONLY
V4.2    Full     12-JUL-1985    NO
V4.3    Update    9-JAN-1986    YES VMS043.A-COMMON FILES / VMS043.B-VMS ONLY / VMS043.C-UVMS ONLY
V4.4    Full     30-MAR-1986    YES (integral part of all Savesets)
V4.5    Update   26-SEP-1986    same as with V4.3 (individual Savesets)
V4.6    Full     15-JUN-1987    same as with V4.4 (integral part of all Savesets)
V4.7    Update   29-OCT-1987    same as with V4.3 (individual Savesets)

That seems to me a rather good proof that MicroVMS versions are 
(at least from V4.1 Update / V4.3 Full onwards) functionally equal
(to the extend possible on MicroVAXen) to the corresponding VMS versions. 

Distribution tapes were identical, whereas the RX50 floppy sets most probably were not (as to save space/floppies).

I'm still looking for the following versions:

- VMS V4.2 MUP (Mandatory Update)
- VMS 4.3A
- VMS 4.5A
- VMS 4.5B
- VMS 4.5C
- VMS 4.6A
- VMS 4.6B
- VMS 4.6C
- VMS 4.7A

Can anybody help ??? 

Has anyone got any MicroVMS V1.0 (= MicroVMS V4.0) media or software ???