"Rollei is a German manufacturer of optical goods founded in 1920 by Paul Franke and Reinhold Heidecke in Braunschweig, Lower Saxony..."
"...1928 saw the production of the first ten prototypes of the legendary twin-lens Rolleiflex..."
"...World War I was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918..."
Maybe another manufacturer was using the periscope idea during the Great War?
I just looked up tlr's on Wikipedia. Rollei was in the 1920's but twin lens reflexes date back to 1870. It may not be a Rollei but an un-named TLR'.