Vertical coil pair
Note imperforate sidesCoil stamps are a horizontal or vertical strip of stamps, usually rolled into a coil, thus earning their name. Historically, there have been two main users of coil stamps. One user is a stamp vendor who sells stamps by machine and would use coil stamps so that a specific number of stamps could be purchased by the user. Mass-mailers are the other main user of coil stamps. They use the stamps so that their automatic machinery can apply the stamps in rapid fire to hundreds or thousands of letters.
The first attempts at mechanically vending or affixing stamps used regular perforated sheets of stamps that had been separated into long strips of stamps. This caused problems because the perforations on the sides would mess up the machines, and the perforations between the stamps would sometimes separate at inopportune times.
The United States Post Office tried to solve these problems by selling imperforated strips of stamps for this purpose. Vendors could then add their own perforations to the stamps for their specific reasons. These private perforations are highly collectible and there are several resources available for determining the company that sold or used the stamps.
Early coil stamps were manufactured from strips of stamps pasted together. For example, a pane of 100 stamps arranged as 10 rows of 10 stamps would be cut apart to make 10 strips to 10 stemps. Typically, every 10th stamp of one strip would be pasted to the 1st stamp of the next strip, yielding a 100 stamp strip. The pasted area of the stamps would remain and would sometimes be used to mail letters. Some of these pasted pairs of stamps have survived and are very collectible.
With the advent of the rotary press, a continuous stream of stamps could be printed. The round die used to imprint the stamps has a seam where the curved stamp plate is joined together so as to be continuous. This results in a faint line on the strip of stamps, since ink tends to accumulate in this tiny seam. The seam is called a joint line, and the two stamps adjacent to this seam are called joint line pairs. These types of coil stamps are also in demand.
There are two orientations of coil stamps -- horizontal and vertical. The vertical coil stamp is where the stamps are arranged top-to-bottom and have the perforation between them. Usually, but not always, this means that the stamps have no perforations at the left or right, yet have perforations on the top and bottom of each stamp. The orientation is reversed for horizontal coil stamps.
Around 1980, the US Postal Service added a plate number to every few stamps in a coil. The plate number identified the printing plate used to create the stamps. This number created a new collectible craze, as collectors sought after these plate number coil (abbreviated "PNC") stamps. Generally, collectors prefer that plate number coil stamps are contiguous strips of stamps with the center stamp being the one with the plate number. You typically see them as strips of 3 stamps (PNC3) or 5 stamps (PNC5)
Self-adhesive stamps, which have die-cut and no perforations, can be sold in coils as well. Currently, many post offices are selling "liner-less" coils, in which the self-adhesive stamp sticks to the next lower layer of stamps, much like how adhesive tape lightly sticks to itself on a roll of tape.
Coil stamps are an interesting variety of stamps to collect.
Previous Terminology Topics:
- Common Design Stamps
- Forever Stamps
- Air Mail Stamps
- Semi-Postal Stamps
- Commemorative Stamps
- Definitive Stamps