I found this rare picture of an unraced Honda RA109 with a 2010 Mercedes livery. Note the sidepods and bodywork taken directly from the RA108 : r/formula1
Honda's Big Surprise - Behind the Japanese manufacturer's Formula 1 Exit
Honda's mystery F1 car - Page 2 of 4 - Racecar Engineering
Sean Bull Design on Twitter: "Alternative F1 Histories... Honda Stay in F1 and develop the car and team: Would they still have won the 09 titles? how would they do in the