Yes, this is a WWI MC in original case. Both the MC and suspension are silver, but of different grades (I believe) and they certainly tarnish differently (in part due to their degree of contact with the case lining which seems to be ratrher toxic). It is hard (but necessary) to resist the tendancy to polish, for that would destroy the history of the piece and replace it with nasty "bling". Numbers? Abbot and Tamplin's excellent research shows 37,081 MCs from the creation of the award in 1914 through 1920. There were maybe another 230 (or so) from then until George V's death in 1936 and the transition to the new George VI design. The whole issue of provenance needs to be treated with some care. The MC was, unusually for British awards, unnamed so you can never be very sure about anything. Some were privately named (but this adds a whole new area of concern). When a medal is in an original mounted group, you have some certainty, but anything else is just an attribution, a story, maybe a fantasy. Value? Not a game I like to play. The 2008 Medal Yearbook (controversial enough in its own right) shows a George V single MC at ?500-550. A case will add a bit, but not a lot. Checking a couple of reliable dealers' lists, I find single WWI MCs at around ?500, cased around ?550. Take this with sone size of grain of salt. Hope this helps.