Engine Head Casting Question What is this Line?

[stickwelder]

What is this line?
I have four engine heads and noticed one has a line across the head the other three don't have. Why is the line there? Is it important? It's the one on the left. Hopefully my pictures show it well. Thanks, Tom

 

[Tom Wesenberg]

I see a casting (mold) line. Must be an aftermarket head. I don't recall ever seeing one like it.

 

[Milton]

Just cleaned off a head today and found a line identical to the one pictured above. So am I to assume that this head was cast after 1931 since I doubt aftermarket parts suppliers knew about a head change in advance of 1932.