What Cockpit?
Polikarpov P2???
Glider pilots are good at arithmetic! The Polikarpov R-5 it is:

https://en.wikipedia.org/wiki/Polikarpov_R-5
It featured in a recent What Aerodrome, hence it looked familiar to me.
866 has control.

https://en.wikipedia.org/wiki/Polikarpov_R-5
It featured in a recent What Aerodrome, hence it looked familiar to me.
866 has control.
The operating arm on the lever goes forward so I think it's the pitch change mechanism for a nose-mounted engine. I see a Both position on the mag switch so presumably dual-ignition.

Prominent lever is indeed for mechanical pitch change. Interestingly for this particular type both UV and I42 are part correct! My uncle Brian in the prototype.
Last edited by asw28-866; 3rd Jan 2021 at 04:48. Reason: Add image
There is a Fournier element to this aircraft, but not an “RF” type. A clue was provided when I wrote that both your initial response and that of UV correct in part.