At least i got the plate and i am very happy about it !
The "finish" is the same all over the badge and all lugs are fixed/soldered in the same way.
The Volunteer Medical Staff Corps got official status in 1885 and was retitled Royal Army Medical Corps (Volunteers) in 1902. (if i am right ?).
So, as Simon mentioned, there is a very short range of time for this badge with the KC, and for me now a nice and possibly rare variant in my small collection of corps badges.
Kind regards
Markus