Unmarked Crystal Glasses

I was given these crystal glasses about three years ago. I was told they are old and made out of pure crystal but I dont know how true that statement is. I have three differnt styles; 4 champagne glasses, 4 wine glasses and 3 scotch glasses. They are quite heavy and I know they arent made with much lead beacause i can do the ole flick test to te brim of the champagne glass and it does not "ring" as compared to another glass I own that is made with 80% lead. These glasses have no sticker or mark on them to let me know the brand or who they were made by and they are very heavy and thick. Any information would gladly be appreciated.