It's a scale model design that includes a rotating stabilizer under the fuselage, one of many concepts that Andre Watteyne explored in the late-1950s/early-1960s for various flying models.
EDIT: It actually might be the other way around; the bottom rotor creates lift while the main rotor stabilizes the model in flight.
-- Edited by Stingray on Wednesday 3rd of June 2020 11:02:37 PM
__________________
lllllAs of 2019 I have transitioned; My name is now Rei. Please don't deadname or misgender me, thank you. <3 lllll