Terry,
Looking at some of our price lists from the 1920s, your Lister's Dental Floss, 10 yards, in a glass container, would definitely be from the 1920s. It appears in our 1923 price list. If you want to send me a picture through the blog's email, I would be happy to compare your photo to the picture of the product in our price lists, and give you a more definite answer. The email is kilmerhouse@its.jnj.com
Margaret