J Head with no casting numbers.

I Had a matching pair of 915 J heads off the same engine.

Both have the "J" down by the spart plug holes but one has no
casting number on it either on the top or bottom of the head.
I was never cast into the head but the area where the casting would
be is blank and never had a casting number in that area.

I believe all J Heads are 915 castings and the head is otherwise identical
to the other one.

Has anyone every seen one before from the factory with no casting number
ever on it?