Show Your Center Line Blocks

Some of the early issues had a horizontal and vertical center line.
Here is my one and only:

Here's mine. Only a horizontal line but with a selvage. Maybe someone can explain what positions allowed for these horizontal and both horizontal and vertical line variations. I've never studied it much. And yes, this is the only one I have, too!

In the early years, 4 plates were placed as a 4-square on a cylinder for printing. Where the two left plates butted against the two right plates, there was a thin gap and where the two top plates butted against the two bottom plates there also was a gap. Each plate printed a pane of 10x10 stamps, so the cylinder printed 4 10x10 panes. Where all of the plates abutted or joined you would get a thin color line. So my block is where the top right, top left, bottom right, and bottom left plates came together on the cylinder. Your block is where the right two plates abutted next to the right selvage.

Thanks. Another interesting bit of information!

Nice Farley's, I_Love_Stamps. I have always liked the Farley's, especially the National Parks issue. Some day I will get them.