Ok, we need to correct some things.
The press sheet of 400 which Studebaker shows is fully perforated except for the red lines down/across the center - THESE are the straight edge stamps - along the central cut lines, not those around the edges of the sheet. The cutting of the sheet of 400 into 4 panes of 100 leaves 19 stamp on each pane with 1 or 2 straight edges.
The original poster's stamp comes from the 11th row of the 400-stamp press sheet, just below the red horizontal cutting line.
Some collectors in the early 20th century reassembled 9 stamps into mini-panes with the guide line around the perimeter. These are attractive (like the black Hardings above), but are incorrectly assembled to the way in which they were originally printed. Accurate reconstruction mounting would be like this, with the lines crossing in the center (colored dot):
(The guide line price guide scan is one I had posted originally.)