What is the head casting code and the head date casting code?

You could have a 1953 head, or you could have a 54 head that has been "converted" to use the older two-bolt valve cover (as Bill posted above).

Are there two screw holes in the head on each side of the valve cover (I do not recall if those 4 holes show on a 54-63 head that is converted to using the older 2-bolt valve cover?