The doll you have is a reproduction of an antique China head doll which collectors refer to as a "low brow," due to the style of the hair. The person who made the doll in 1975 (Della/Delta Nector/Hector) signed the back of the doll's shoulder plate. That may be the only doll she made. Back in the '70s and up until the early '90s, there were many businesses throughout American cities where a person could go in and, for a fee, take a class to learn to make a doll. There would be molds to choose from and all the needed materials (greenware, a kiln, various tools, etc.) as well as paints and doll clothing patterns, to produce a doll. Like any other hobby, people had varying degrees of skill in painting the doll's hair and facial features. Some people were very skilled seamstresses. I think your doll is made of ceramic, rather than a finer porcelain. If you look at the eBay section for "reproduction antique China head doll" you will get an idea of what someone would be willing to pay for that sweet circa 1975 doll.
