This Scott #5873 caught my attention. There is a deviation in the horizontal die cuts.
The deviation is most noticeable below the letter "R". Though difficult to see, there seems to be a matching deviation at the top edge of the stamp.
The stamp's physical height measures precisely 25 mm. I consistently measured the height of 25 mm near both the left edge and the right edge of the stamp.

(I digitally added the pink rectangles as a visual assistant.)