Additional information - Supplied by John Proffitt

This information was obtained from "Goldhor's Blog" in Germany:

Up to the fall of 1944, according to Helmut Krueger, about 250 stereo recordings had been made. Among these were the opera Romeo and Juliet, Margaret, Tosca, Tannhauser and the Mastersingers, each in Bayreuth in 1943 under Hermann Abendroth and 1944 under Wilhelm Furtwängler. As the Allied air raids on Berlin intensified in late 1944, the valued equipment and tapes were moved to the Central Laboratory of the Reichsrundfunkgesellschaft (RRG) in Wartheland (eastern Poland) for safe storage. Hans Joachim von Braunmuehl, the future head of the SWF, organized music evenings for the doctors at a nearby military hospital there, using the RRG tape recordings and equipment for entertainment (!). At this point, with the rising chaos of the end of the war, further tracing of the RRG stereo tapes and the equipment is impossible. Only five stereo recordings of the RRG probably survived the turmoil of the last days of the war.

John Proffitt adds, "There are several other German-language blogs and articles relating correspondence and conversations with Krueger, which seem to substantiate the number of 200 – 250 stereo recordings by late 1944."