Locating the Plate Number on the British Penny Red Postage Stamp

Illustrated below is an example of the British Penny Red postage stamp. The plate number is located on the side of the stamp within the linear curves running down the edge of the stamp, The first example shows the plate number 157. The second example shows the plate number 160. The numbers can be located on both left and right edges of the stamp. Plate numbers were introduced on April 1st 1864.