You probably should note further identifications in the "Ebay Categories" Forums instead of this Selling one - here is the standard history for you. It would have been greatly valued in the early 1930s - unless you collect Bavarian - not so much any more.
This R.C. Rosenthal backstamp/mark dates this mug from 1898-1906.
Philipp Rosenthal (1855-1937) began business in Germany in 1884. Initially he purchased white ware from the company Hutschenreuther which was resold door to door after being hand-painted by his wife Maria. In 1891, he established a factory in Asch, Bohemia and began production of his own white ware. From 1897 to 1934, Rosenthal acquired further factories in Kronach, Marktredwitz, Selb, Waldenburg, Sophienthal, and Waldershof. The Marktredwitz factory acquisition in 1908 included the full brand name.
