Rupert Habermayr was located at Ludwigsplatz 35, Straubing/Bayern in the 1930’s and 1940’s. (per Pape and Kellners archive). In 1924 he applied for a Austrian patent for a Game Call which was issued as AT101713B in 1925.
The following images were found in Dietrich’s archives and are from Mr. Al Rickli and show a Double Rifle Drilling serial no. 19358 which was proofed in 1938. It was chambered for 6.5 x 57R, 6.5 x 57R and 20 ga. by 170mm and had automatic ejectors.