From the ebay ad:
G. MOLLENHAUER &SOHNE KASSEL curved basset horn in C prototype (only one piece ever made) - in excellent playing condition. This instrument was never actually produced and sold commercionally. Free of cracks on the wood or repairs. All original. Pads are in good condition. No previous repairs. Keywork and mechanic in excellent condition. Excellent intonation. Recently checked by technician. In tune and ready to play. Professional level, key:C, modern pitch - 442Hz, body material alpine maple wood, range down to C, silver-plated keys -100%, key system- Albert (German), undercut tone holes, high-78cm. inner bore-29mm. second small bore-21mm. bell diameter:12.3cm. The bores are united at the bottom with a U bend of wood. Including floor peg, original hard case and Hammerschmidt Klingson No.2 mouthpiece. Crafted in Germany as prototype (only one piece ever made) ca.1970's.