The caseback is prior 1949 because there is no date mark stamped on the back, and the slender rectangle shape with the round dial looks to be mid to late 1930's or early 40's. If the case is hinged it would be late 20's early 30's
The movement will come out of the caseback, but may need some very gentle prying all the way around it with your fingernail between the movement (dial) and caseback. There will be a symbol stamped on the movement, usually along the edge that will date its production, which is key in trying to ID it.
If you are not comfortable in trying to remove the movement from the caseback, take it to a qualified jeweler for help.
Here is the link on date symbols and where to find them on this site. http://www.mybulova.com/bulova-date-codes
Greg