I have a valuable beer stein that belonged to my German grandfather (he died 1927). It was altered by him (I believe). The stein is an 1894 Mettlach Anheuser Busch Stein #2136. However, the top of the lid with the AB image was crudely cut out and replaced with a piece of clear glass. My question is what is its value, given this alteration? It is otherwise in excellent condition. (I would attach a photo but not sure how to do that here.)
The original in mint condition would be in the range of $2,800 to $3,500 in mint condition. The replacement, which you describe as crude, would seriously reduce its value. A stein auction company would have a better idea, but I suspect you are looking at under $1,000. You might be able to get a replacement lid or repair, but it will not restore it to mint condition.