Signed portrait of the important conductor, friend and advocate of Mahler, Strauss, Schoenberg and Reger. Vintage sepia postcard photograph of Mengelberg in a head and shoulders pose, signed 'W. Mengelberg' in bold, dark fountain pen ink across a clear area at the base of the image and further signed and inscribed to the verso and dated Frankfurt, October 1910 in his hand. 8.5 x 13.7 cm. Very fine.