I had never seen a Russian indirect sight either. I believe the first use of indirect fire using machine guns was during the Russo-Japanese war in the very early 20th Century so I know the Russians had experience with that technique. The British used dial sights (and/or clinometers) for indirect fire extensively in WWI and in WWII. It would be interesting to know how much Russia used sights as panoramic and indirect sights both seem to be rare. While the US developed a panoramic sight for the M1917 Browning during WWI, I do not believe they were used very much and I believe they were dispensed with entirely in the early 1920's. I am aware that both the Japanese and especially the Germans utilized panoramic sights. Happy to hear from a more knowledgeable forum member on this subject.Now wouldn't that be a cool accessory to have on the Maxim.
Thanks for posting it, I never knew they existed.
I won't ask about the value of one, I think I answered that question myself.