Both of these issues have a number of varieties, but of the two the design inscribed "U. S. POST" is by far the most interesting, and any philatelist who devotes some study to this, the "spoiled child" of the Post Office, will quickly be fascinated with it. Indeed, a fine collection of these die varieties must be a revelation to those philatelists who have, so far, kept aloof from collecting them under the specious plea that such collection required too much study and labor, and the differences were mere gossamer threads woven by the overwrought imagination of some wild enthusiast. It is undeniable that until recently the multitude of Jackson varieties--unclassified and jumbled together as they were--did not present an inviting field for the general collector. But that difficulty has now been overcome, and we have the various designs grouped into distinct classes, which even an untrained person can recognize at a glance.
Those who possess a number of Jackson dies cannot have failed to observe that in various specimens the forward end of the bust points to different letters of the word "TWO" in the lower label. It required no great amount of ingenuity to examine all known varieties of this die, and to reach the conclusion that this important feature should be selected as one point of a line measurement which would subdivide the varieties into distinct classes. In carrying out this idea it was equally apparent that in order to draw a straight line we need two definite points, but the problem was: which point would serve our purpose best? Luckily the design lent itself admirably to the construction of such a line and the second, or starting point, was found in the point of contact of the right hand oval with the inner frame line of the upper label. The line is, then, drawn from this point to the left extremity of the bust and prolonged until it strikes the letter "W" or "O" of "TWO." In this manner five definite and unmistakable classes are established, each of which may contain a number of varieties. While this system is indispensible for classification, the collector, after a very little training, may omit the actual line measurement, as the eye is sufficient to note the class to which any variety belongs. The five classes are: