Hello,  following on from the other nights post I thought perhaps this might be of interest. Two more differences for you to look for, if you have the patience and an eye for the detail, in the 2^nd class Machin NVI (No Value Indicated) stamps.

The crown on the stamp to the right has a larger distance between the edge of the crown and the right hand edge of the frame.

From my reading this is because the right hand stamp was printed from a chemically etched process and is from a 1995 issue, while the left hand stamp was printed from an improved computer engraved method and is from a 1996 issue. 

The most obvious difference perhaps is that the Queen’s head image is much sharper with a higher degree of definition on the left hand stamp.  I welcome comments and correction perhaps from readers with more knowledge than I have.

Anyway, perhaps like me, you enjoy and find it interesting to look for such differences.

Enjoy your stamps..  Best wishes….. Michael      cddstamps.com