“The perfect ventriloquist or the most appropriate method to learn the ventriloquy in the shortest possible time and without fail” is an instructional booklet by Jaques de St. Gillé, published by Ficker’s Verlag in Leipzig, Germany. Auktionshaus Zeiler has an image of an older edition from c. 1900 where the Jugendstil decoration is shown in full splendor. This modernized version is probably from the 1920s. The main illustration was maintained, but the floral framing had to go, and the lettering made way for Bernhard-Antiqua (1911).
It’s not clear if the author is the same Monsieur St. Gille as the grocer from St. Germain-en-Laye whose astonishing skills were described by M. de la Chapelle in Le Ventriloque (1772), see The Cyclopædia: Or, Universal Dictionary of Arts, Sciences, and Literature by Abraham Rees (London, 1819).