Hi Bob your doll was produced from about 1888 – 1931 in 1931 the company went bankrupt. Charles M. Bergmann operated a doll company in Waltershausen, Thuringia, Germany. Their dolls were distributed in the United States by Louis Wolf, who also registered several of their trademarks for them; Baby Belle, Cinderella Baby, Columbia, Eleonore and Spezial. Bergmann dolls came in sizes from 10″ to 42″ tall.
So I would research Louis Wolf who was the US distributor and registered the trade mark of spezial for them. Then you can pin down the year this doll was made. good luck