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130296019712Air-cooled aircraft(?) radial, cylinder, head & piston.
My first thought was a Wright R-975 (as also used in the Sherman tank)
because the exhaust side is so much more heavily finned than the
inlet. However it looks wrong for that. Could it be a Kinner?
I think we can agree on the "UNKNOWN MAKE POSSIBLE ROLLS ROYCE. " part
though 8-)