Hi Wenda, would it be possible to see a picture of your rabbit please so we have some reference to refer to in the future?
Inca will surely be correct about it being M as she knows so much about this glass.
I have a couple of these, but not in blue. One with a sfumato finish says FM Ronneby Sweden M 506, the other is Marcolin Crystal, all black with Marcolin Sweden C9 on the base. I will take some pictures and post them here and hope you will do the same, that way we will have all the rabbits in one rabbit run!!
As for value, best look up completed sales on eBay...as Sue says, they are worth what they sell for.