Ok, then I'll start and hope nobody mind, that this apparatus, which really was a
flying machine and no combined harvester didn't fly before 1920, so not exactly in the
1910 - 1920 era.
It is the Helicopter N°2 built by the frenchman Etienne Oemichen and first flown
in 1922.
Although it is generally called one of the first helicopters, it actually is a VTOL
design, because it is a compound and forward motion is achieved not by the four
rotors, but by the eight propellers.