having looked at the back...just to hedge my bets...it may only be a green crystal...an emerald had a deeper colour to it...as to the metal...just because it does,nt have a hallmark...does,nt mean..it has little value...it could be silver...but without a hallmark...but...wi th no mark..it is then classified as...white metal....subsequent ly...value..is then limited...i,ve seen some on ebay..ranging from..£3.50....to £16....but..if its not eaten a lot of your corn...then wear it and enjoy it....