Steinzeug-krug (or stein)

In an effort to help a fellow German persona with their research, I'm looking into glass beer steins from 1485.

So far what I've found is an exerpt from The Beer Stein Book: a 400 Year History, 3rd edition, 1999, Glentiques, Ltd, Coral Springs, FL, which indicates that beer steins (which are covered mugs or mugs with hinged lids) started after laws were passed requiring that all food and beverage containers be covered to protect consumers against flies and other such germs and diseases. These laws were passed due to the effects of the Black Plague (1348-50) on the various populations around Europe.

From what I can tell from this article, well to do Germans up to the 1400s had pewter beakers, silver vessels and even some made of glass, but they were too expensive for the general public or for large containers. Wooden and porous eartheware were used, but they tended to break fairly easily and absorb the smells of the beer. Tho stoneware at this time took longer to make, it became superior to earthenware because of its resistent to chipping and cracking and its not porous, resulting in a much more sanitary container.

I believe it's safe to assume that since they make glass steins now and that glass tankards were made before the passage of the laws in Germany concerning covered beverage containers, that glass steins were likely made in 1485. I'm unable to find the exact date of the passage of the covered beverage law, but considering glass was used before and during the Black Plague of 1348, I would see it as reasonable to have been used.