In the early 1970's, Gyula Foky-Gruber in Vienna developed the "Silberton", an all-metal soprano recorder made entirely of nickel-plated brass, and an alto made of rosewood with a metal head-joint and two keys for the lowermost finger hole. Both featured a sytem of adjustable voicing achieved by altering the position of the block and the height of the windway. Both were of cylindrical bore. Later the German firm Hopf produced "Silberton" instruments which they now offer as "Gruber System" recorders by Kobliczek in sopranino, soprano, and alto models. Today, Gruber is making them again by himself as signed handmade recorders in small series, also in pure silver.