seam where ink tends to accumulate, resulting in joint line pairs. Perforations 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"). Longer perforations on one side than the other, and separation by cutting rather than tearing, are indications that a stamp may have come from a coil. Recent innovations A recent innovation enabled by self-adhesive technology is the linerless coil stamp. While most self-adhesive stamps 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. See also 1935 Irish 2d coil stamp An experimental Irish stamp. Plate number coil Coil waste References Further reading Armstrong, Martin A. The Coil Issues of the United States, 1906-1938. Lawrenceville, N.J.: M.A. Armstrong Enterprises: Trenton Pub. Co., 1980 124p. Jaffé, Hans H. and R.E. Kuntz. Coils: A Worldwide Catalog = Roulettes = Rollenmarken. Cincinnati: H. Jaffé, 1980 84p. Rudd, Charles D. Coil Stamps: Introduction, Development and Uses. Christchurch: Selwyn Stamps, 1995 89p. External links The £sd Postage Stamps of Great Britain Issued in Rolls Philatelic terminology