Perforation key
With the help of a perforation key you can determine the perforation of a stamp . It is one of the most important tools for philatelists .
Optical aids
Such a toothing key is made of cardboard , plastic- laminated, printed paper or metal . The most important perforations of postage stamps are drawn on it. For example, with a 10 degree of perforation, there is a spacing line every 2 mm. This then corresponds to 10 tooth tips and 10 holes over a length of 2 cm. A good serration also has subdivisions, which are then indicated as serrations with fractions (e.g. 12¼). The spacing bars are usually white on a black background, as this makes it easier to identify the appropriate size (the teeth on postage stamps are usually white and stand out much better against a black background).
To determine the perforation of a stamp, the stamp is pushed back and forth on the individual scales of the serration until the individual tooth tips fit exactly on the spacing lines or all perforated holes are congruent with the "holes" drawn.
Cardboard toothing keys are almost no longer used today because they can be damaged too easily.
Mechanical-optical aids
Such teeth wrenches are either made of plastic or metal, with the most important degrees of teeth being shaped as small combs. With such a measuring device it is not only possible to carry out a purely optical check by shifting the marks; it also allows a mechanical check by sliding the mark against the teeth of these combs. If the stamp is everywhere on the comb, the correct perforation has been determined.
When using such a serration wrench, however, particular care is required, especially during the mechanical inspection, since the marks can be damaged if the serration comb does not fit.
Electronic measurement devices
Electronic perforation meter is the name for an electronic measuring device with which philatelists can determine the perforation of postage stamps in an automated manner. SAFE Schwäbische Albumfabrik GmbH & Co.KG sells one such under the registered brand name "Perfotronic" .
Measurement
The stamp to be measured is placed on a measuring rail and fixed with a transparent positioning aid. After starting the measurement by touching a sensor switch, a motor-driven light barrier moves along the rail. The light / dark changes that occur through the perforation of the applied postage stamp are amplified and evaluated by a microprocessor. The result is rounded to the quarter values specified in the catalogs and shown on a display after the end of the measurement. With the "Perfotronic 2" model, the result can be set to 1/10 or 1/100. A measurement process takes approx. 5 seconds.
Advantages and disadvantages
The greatest advantage of the electronic serration meter is the speed and reproducibility of the measurements. In the case of a mark with marginal perforation (11 or 11¼?), The device always determines the same result. Even if the perforation has to be determined for a large number of stamps, the electronic perforation meter is superior. The manufacturer's high list price makes the device interesting and affordable only for special collectors or collectors' associations. The device is dependent on a socket, battery operation is not provided. This means that the electronic serration knife is usually unsuitable for attending trade fairs, exchange events or the like.
Computerized measuring devices
There are computer programs from various manufacturers, but mostly only together with a microscope that can be connected via USB . With the programs, these optical recording devices are able to measure the perforation with great accuracy; in addition, other properties of postage stamps (e.g. colors) can also be determined. The disadvantage of this method is the complex calibration that should be repeated at regular intervals.
Web links
Operating instructions (PDF; 547 kB) for the "Perfotronic" from SAFE
literature
- Norbert Röhm: The oldest philatelic system: 125 years of perforation. In: Philately No. 200 / Philately and Postal History No. 121, November 1991, pp. 36–46