I've never even thought about it.
"Technically, the United States has not issued se-tenant coil stamps.
"Since 1981, U.S. coil stamps have had small printing plate or cylinder numbers printed at the bottom of individual stamps in the coil at designated intervals.
"Many collectors consider a plate number coil single stamp to be a face-different stamp when compared to the same coil stamp without the plate number.
"One could say, then, that a pair of coil stamps, one with a plate number on it and one without, are se-tenant.
"The United States has also issued self-adhesive coil stamps with different designs, such as the 1993 and 1995 Christmas stamps, each with four different designs. However, the stamps are die-cut and separated, not attached to one another, and cannot properly be defined as se-tenant, unless the backing can be considered as holding them together."http://www.linns.com/insights/stamp...ogether.html