Quoted from JReedie:
My first pinball machine is the EM "Queens Castle" from 1978. I'd love to know how many were made as later on in 1978 the game was turned into the solid state "King of Diamonds" so can't be too many of them kicking around surely?
I'm not sure... they're quite uncommon and I've never seen one in person. Well, not until next Tuesday when mine arrives.