Quoting directly from Sailboatdata.com:
“The NATIONAL 10 class was originally known as the TURNABOUT CLASS, built in 1953 by Harold R.Turner as a small wooden single or double handed dinghy class. Many boats were kit built by “do it yourselfers” in their garages or cellars.
The boats were initially built as a junior training boat, although adults enjoy the boats as well. The class has grown mainly in the New England and Northeastern regions of the U.S. Fleets are located in Northern Lake George, New York, Boston, Massachusetts, Rhode Island, Maine and New Jersey.
In 1972 the TURNABOUT CLASS formally changed it’s name to the “NATIONAL 10″ class. It also decided to refine the class by approving a new mold, designed as close as possible to the original wooden design. This was accomplished by J.R.Duplin Marine in 1972, with some major improvements, including aluminum spars. The minimum class weight of 215 lbs was increased to 255 lbs. to keep both the older Parker River turnabout, the woodies, and the new Duplin National 10’s more competitive.”
Read more at Sailboatdata.com.