Claim: Oberlerchner Mg 23 is an all-wood, high-performance sailplane that was first flown in Austria in 1955.
Evidence: The Oberlerchner Mg 23 is a single-seat, all-wood, high-performance sailplane. It was built and first flown in Austria in 1955, and a total of 26 were built before production ended in 1965. 
Single seat high performance sailplane Austria 25 June 1955 (Mg 23 prototype) The Mg 23, an Erwin Musger design often known as the Musger Mg 23, was an all-wood shoulder-wing aircraft.