This is an extraordinarily rare buckle, of which I am only aware of 3, including this one.  Many believe it is a prototype buckle designed to replace the SA Buckle.  Others believe it was produced exclusively for wear by Hitler (there is photographic evidence).  Whatever its true purpose, it is rare.  Diameter is approximately 45 mm, is produced in a solid construction, and retains a large portion of the silver wash.  It is cast or die struck in a heavy metal such as white brass.  This specimen is fresh out of the woodwork and has not been in a collection.  Identical to the 2 examples pictured in the Angolia book on buckles.