This is a modern or contemporary stein, meaning post WWII and is probably worth no more than $20-$25. My guess would be it is from the 1970s-1980s. The scene depicted is the pre WWII skyline of the City of Mainz am (a.) Rhein (Mainz on the Rhine) and the Dom, or the Mainz Cathedral. Mainz is located at the confluence of the Main and Rhein Rivers. Construction of the cathedral began around 975 and the main portion was completed about 1037. The cathedral was heavily damaged during WWII when in August 1942, after an allied air raid on the city. Restoration of the cathedral began following WWII and was not completed until 1975.