It will be observed that no one stamp is known with all three varieties of perforation, except the One Penny, bright rose-red, on the unwatermarked paper, and it is not at all certain that all these varieties existed together in any one of the seven different printings that were made of this stamp. Another point we may also note is, that whenever a stamp is to be found with the compound perforation, it also invariably exists with one of the two simple ones, but, with the above exception, never with both. Our second plate of illustrations consists of six groups of four unsevered stamps each. These are intended to illustrate the various perforations of the A and B machines, and as these are more easily studied on the reverse side than on the face of the stamps, it is the backs of the groups we have had reproduced. Nos. 16 and 17 show the work of the A machine at two different periods of its career. No. 16 is a group of four of the One Penny of 1861, when the perforations made by the A machine were _blind_; and No. 17 is a similar group of the One Penny of 1871, when the pins generally pierced the paper. These particular groups were selected by us for illustration as showing a very marked contrast between the character of the perforation of 1861 and that of 1871; but as regards the latter, it is not easy to find such long lines of perforations in which _all_ the holes are pierced through, as in the example we show in No. 17. In these two particular instances, if the central lines of perforation be gauged, the vertical line in No. 16 will be found to be 14 at the bottom and 14½ at the top. Its horizontal line is 15 on the left and 14½ on the right. In No. 17 the vertical line is 14½ at the bottom, higher up it is 15, and at the top it is again 14½. The horizontal line of No. 17 gauges 15 throughout its length. It will be noticed that in no one of these four lines do the two extremes of 14 and 15 both appear; but it must not be inferred from this that such is never the case, and we have now before us a group of four of the Six Pence of 1871, in which both gauges of 14 and 15 are present in the same line, and actually overlap each other. This group would not, however, have been so suitable to illustrate the general character of the A perforation in 1871 as the one we selected, since the holes in it are only pierced through in parts of the lines.