Though you missed a bit out of the title:
ROOOLS ROYS MELRIN ENGEIN (NOT XUD, GRIFFIN, PACARD V-1650, METOER, EURPORP TP400, SECMA OLYPMUS 593, DIAMLER-BENDZ DB 601A, BORA, A3, 320D)

Try a specialist forum ( merlinoc.co.uk ?) who might be able to point you in the right direction of a lookup of the serial number.
The first picture I thought it was a fossil that had washed up

Love the art deco nameplate though, they just don't do that on engines anymore.