Interesting that this elderly thread replicates the "which blads have the Gliding Mirror" question which is a regular.
The later models that do not have it like the 553ELX and 555ELD (perhaps because of the way the built in motor operates) allegedly have a longer mirror (now how they manage that and why they didn't do it before I have no idea) the 501C does not have GMS ( the 501CM does) but I'm not clear if it has the longer mirror if it exists.
I have placed a query with Hasselblad Support, which generates a "ticket number" asking the question, replies within 24 hours. Three days later the ticket has been removed and is not answered it may be they are so fixated in X1D that the staff can't spend time on heritage support or indeed there are no staff left in support to assist with "V" questions. sad really as my V will be operational long after the X1D has become recycled.
It may be that the GMS and the non-vignetting mirror are confused, the catalogues of the time show the GMS came in 96/97 time but I see no mention of a "non-vignetting mirror".
This source states all models mentioned have a non vignetting mirror but the GMS, not fitted to some of those ticked, is not mentioned.
https://www.bhphotovideo.com/FrameWork/charts/comp_hasslbmed_5.html