Oppama thank you for all you help.

Kanji remains difficult for me to understand and I rely upon Google translate, Kanji drawing programmes and Chinese/Japanese colleagues for assistance.

So to conclude this is a Nakajima Sakae piston with a bore of 130mm – liberated from a crashed aircraft.

The bore and design suggest it is from a Sakae 12 as used in a variety of IJN and IJA aircraft ?