California artist Otis Oldfield studied at the Academie Julien in Paris, France. Upon his return to California, according to a biography on AskArt.com, he rented a studio in San Francisco's old Montgomery Block and became an instructor at the California School of Fine Arts. He was at the school from 1925 to 1942 and received a Gold Medal Award for Graphic Arts. A major figure on the San Francisco art scene, Oldfield was chosen as the art supervisor for the Coit Tower lobby decoration.
It is likely that this watercolor dates from his Montgomery Avenue days as the backing material gives his address as 1405 Montgomery Ave., San Francisco, Cal. It also gives the title as "Crabber" and indicates it is "No. 173."