German stoneware pottery beer stein w/ grouse, marked West Germany

Unusual grouse design on this vintage stoneware stein, all hand-painted, we think?

It's marked O S L, West Germany, with a B in an arrow mark. (We have no idea as to the maker or the exact age of this piece, sorry!)

The stein measures 5 1/4" tall, and is in excellent condition without damage.