Started by Eduard Bay in 1933; note that it's not correct that Bay stopped art pottery production in 1971; some art production continued into the 1980s, including some striking works...some not so striking; Bodo Mans; Bay was one of the top early companies with decors such as Florenz (1955), Rheims (1960), and Ravenna (1961).Bay continued to make some excellent items through the 1960s as well as some lesser lines, but slipping demand for art pottery forced a change to kitchen items.
In the era from 1954-85, well over 100 German companies made collectible art pottery. So this is really just a hint and should not be taken as anywhere near all the answers.
I would make sure to list it in all the major cities.
If I can be of any further help or if you have anymore questions, don't hesitate to contact me.
If you do send an e-mail, include a picture of the item and the bottom.
There's not much I can do with only numbers and a description.