Within the EAA (Experimental Aviation Association) a boxer engine with two horizontally opposed cylinders called RMZ-500 has been made in Russia.

“RMZ-500”

-It seems that the pistons are double graduated.

-The RMZ is a Rybinsk factory.

From Appendix 12: It is the Rybinsk Motors factory. The 640 Buran snowmobile engines are a singular success among fans of light experimental aircraft.

“640 Buran with fan and propeller”

“640 Buran cross-section”

“Seen from the other side. Note mechanical gearbox” (PiP = SP)

“Front view” (PeT= SP)

“Another application for the propeller” (PeT=SP)

“On a motorized trike”