The design of the Horten 229 calls for three flaps on the trailing edge of each wing. At least one published picture of the wings at the Smithsonian's Silver Hill storage facility shows a stack of flaps next to the wings. They appear to be aluminum consistent with the below. They are currently not out on display with the wings at Udvar-Hazy. No effort has been made to correct the below based on that information.
"They offer on the left elevator, which originates from the prototype construction for hoards HO IX, also known as HO 229 or GO 229. This aircraft was a revolutionary twin-bladed flying wing, designed by the brothers Horten from Bonn. From 1944, the production was relocated to Gotha, towards the end of the 2nd WK, the machine was further developed by the Gothaer engineers to a larger range with larger max. Speed and max. To be able to achieve bomb load. Especially in the wing and elevator sector, serious changes were to be implemented within a short time immediately before the end of the war. Only 3 machines of "Hitler's Wonder Weapon" were completed.
Actually, the elevators or outer flaps of all HO 229 (V1 / V2 / V3) were made of wood, but by decision of Nov. 1944, in the spring of 1945, only two reinforced experimental rudders made of duralumin were produced. For a long time these were considered lost. The 1945 captured by the Americans "third" machine HO 229 V3, which is now in poor condition in the States, has wings made of wood which, however, are no longer mounted.
The offered elevator was made in the spring of 1945 in the "Gothaer Waggonfabrik", but disappeared in the turmoil towards the end of the war. It has been proven that only 2 copies are made, both for the left side. The offer also includes approximately 80 copies of historical drawings of the outer flaps and rudders, on which the "pilot rudders" can be seen."