These were introduced to the Machin series in 1993. The ellipses were designed to help to deter any attempts of forgery. The elliptical holes are on both vertical sides of the stamp, roughly three perforations in length, they vary in shape from one printer to another.
Unfortunately some clever forgers managed to get round this as several forged booklets of 1st class gold stamps have come on to the market, the ellipses are quite perfect although the stamps are easy to identify as they are a dull bronze colour and are a very poor standard.
See the image right. You will also notice that the matrix on these stamps is intact, whereas on the genuine booklet it is removed.
The easiest way of describing ellipses, is there are two basic types, we can call these ellipse 1 and ellipse 2.
Harrison and Walsall printings are normally ellipse one, these are wider than some of the Questa Printings referred to as ellipse two.
but saying that some stamps from Questa printings have also been found with both types of ellipses.
It has been said that ellipse 1 resembles a the shape of a rugby ball and ellipse 2, a sausage or cigar shape. These have also been described in certain quarters as ellipse R (Rugby) and ellipse S, (Sausage).
Keep em peeled
It always pays to check everything (my favourite saying) including the ellipse type. You may or may not know but combinations of both types of ellipses have been reported on the same stamp, also they have been discovered inverted (at the top the stamp).
Because of the rarity of these particular items they are beyond the scope of most catalogues, but I think it is well worth a mention. One never knows ones luck, a find like this could be worth a small fortune.