C1 - Head Embossed "X" code

[Brad K.]

This question may have an answer in the archieves, but I cannot find it.
Are the "X" numbers (ie: X59) embossed onto the outside of a cylinder head an indication of the actual year date-of-manufacture or are they simply a random mold identification number?

[Jerry C.]

Re: C1 - Head Embossed "X" code

I think the only X head that can be seen on an assembled engine is 1958. It will show X58 on the outside of the head.