I'm a little late to the thread but I thought I'd amplify Rod's reply.
As usual, Rod is spot on
Sometimes because of the location of the overprint or a cancellation, it can be difficult to count the shading lines.
Another way to check is to look at the frame lines. Die 1 (on left) has the inner frame line closer to the solid background than a Die 2 (right). The outer frame line is noticeably thicker on a Die 1 than the inner frame line of the Die 1 and the frame lines on a Die 2'