Coil stamp
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A coil stamp is a type of postage stamp sold in strips one stamp wide. The name derives from the usual handling of long strips, which is to coil them into rolls, in a manner reminiscent of adhesive tape rolls. A large percentage of modern stamps is sold in coil form, since they are more amenable to mechanized handling in large quantities than either sheet stamps or booklet stamps.
Coil stamps first appeared at the beginning of the 20th century. In the United States for instance, vending machines companies began to experiment with the automated dispensing of stamps. Early efforts to break sheets into strips manually did not work well, since they were prone to tearing and jamming, and soon the companies began to request imperforate sheets from the post office, cutting those into strips and punching holes of various shapes between each stamp. A variety of these "private coils" is known, some quite rare. The first government-produced coils appeared in 1908, produced by pasting together enough imperforate sheets to make rolls of 500 or 1,000 stamps, cutting them into strips and perforating between.
Later a rotary press was adopted, which eliminated the pasting stage. The cylindrical plate used on a rotary press has a seam where ink tends to accumulate, resulting in joint line pairs.
The perforations of coil stamps are usually found along the right and left sides ("vertical perf"), but they have also been produced with perforations along the top and bottom ("horizontal perf").
A recent innovation enabled by self-adhesive technology is the linerless coil stamp. While most self-adhesives have backing paper, linerless coils are like a roll of adhesive tape. Such rolls tend to be enormous, with thousands of stamps, and tend to be used only by large mailing operations.
While in most countries coil production is restricted to the workaday stamps used in large quantities, Sweden has produced coil versions of most of their stamps since 1920.