"Living outside Philadelphia has given me opportunities to study many Joseph Henzey made Windsor chairs as well as some from Lancaster County, PA. I can't prove this statement but I do believe that I have measured, photographed and studied more Henzey-made chairs than anyone else. In the case of one particluar early Lancaster County sack-back I disocvered at the Reading Public Museum in Reading, PA, I have seen and studied 5 other sack-backs made by this same unknown Lancaster County chairmaker. There's an article or two to be written about these chairmakers and the evolution of their handiword skills and the development of their sense of Windsor style."
A Windsor chair is a chair built with a wooden seat into which are fixed the backrest and undercarriage. Typically, the backrest and sometimes the arm pieces are formed from steam bent pieces of wood. (more here)