You can find an image of what may be a smaller version of your Dunbar cobalt glass pitcher on the Museum of American Glass website. The pitcher there is decorated with hand painted tomatoes and was made in 1947. Check out the site to find more information about glass.
Dunbar Glass operated in Dunbar, West Virginia from 1913 - 1953 and was Flint Dunbar until the 1930s.
You may also find information online at the Corning Museum of Glass. Visit some glass shows to learn more. You'd be surprised at how many glasses shows there are in many parts of the country. Visiting a show will help you learn about current values. You can also hunt online sales sites. Check with them often as inventories change from week to week.