Perhaps the author of this work is an American artist Ruth Byuol (Ruth Buol, 1897 -?). On her most know very little. Since the early 1950's it is engaged in design, jewelry and ceramics. Products of its work available in the network frequently. However, the site
http://www.omahacityweekly.com/artic...rt-spoken-here said that she, at least in the 1940's he worked and easel painting. Signed it found only on ceramics - see Style it seems to me similar to those in your picture (especially the last two letters). It should nevertheless take into account that the raw clay to sign - not that sign now.