There is some humor in the fact that the first stamps were issued by Great Britain, yet it remained for an Irishman by the name of Henry Archer to hit upon a machine in 1847, "whereby the stamps might be separated without the necessity of using knives or scissors." This was a rouletting machine designed to pierce a series of cuts through the paper in the white space between stamps. Though the idea was excellent and was tested by the British, it was not until 1849 that Archer perfected the device.

Perforations take many aspects, but can be actually grouped into two forms. The one most widely used embraces the forms which remove small pieces right out of the paper. The other takes in the form which cuts into but removes no paper.

In perforating there are two basic types of operation: line and comb. In the former the holes are made in parallel lines vertically and then horizontally. This is the form used by the United States Bureau of Engraving and Printing. The second style calls for the perforating of three sides of the stamp at once, the machine producing one long row of holes and a number of short ones, equal to the width or length of the stamp, and set at right angles to the long one. The sheets have to pass through the perforator only once as the fourth side of the stamp is, of course, perforated at the same time as the three sides of the next row.

Perforations are usually rounded, but they are also made with square holes, rectangular holes and lozenge-shaped holes, as well as pin-point impressions.

Coil stamps are kept imperforate at top and bottom, or at the two sides, with perforations on the two other sides, as the case may be. This makes for smooth operation in removing the stamps in strips from the vending machine.

Perforations vary in. gauge, the catalogue listing being the number of perforations which can be counted in the space of two centimetres. There are special perforation gauges sold for the convenience of collectors, which have all of the gauges to be met with. Sometimes stamps have different gauges on two, three and four sides. The Scott catalogues usually give the top measurements first and then those of the sides of the stamps. Perforations play an important part in the value of a stamp, too.

In addition to perforations, there are those forms of separation known as rouletting. These cuts exist in lines (perce en lignes), arc (perce en arc), serrated (perce en scie), wavy (perce en serpentin), and diagonal diamond-like cuts (perce en losanges).

In considering watermarks the 50-cent U. S. stamp of 1912 was used as an example. The copies with a single-line "U.S.P.S." watermark are priced at $30.00, and those with a double-lined watermark are valued at only $15.00. yet two years later the stamp was again issued, in the same color, and with the single-lined "U.S.P.S." watermark, but perforated 10 instead of 12. This stamp is valued at $45.00. Thus one stamp, depending upon watermark and perforation, can be worth $15.00, $30.00 and $45.00. Such differences are worth some time for study, and lack of knowledge can be expensive.