Plate number coil

A plate number coil (PNC) is a United States postage stamp with the number of the printing plate or plates printed on it. The plate number typically appears as one or more small digits in the margin at the bottom of the stamp. The plate number may be centered or, on some coil issues, located toward the right. Although most plate numbers are composed of just numbers, both a combination of letter and number may be used. In the case when a letter is represented in the plate number, an upper case letter usually appears at the beginning or at the end of the sequence with the former serving as a good identifier of the stamp printer.
The plate number is on one stamp out of the number of stamps printed by a single revolution of rotary printing press used to print the stamps.

Postage stamp booklet

A postage stamp booklet is a set of one or more small panes of postage stamps, usually totalling about 10–20 stamps, folded over and placed in a cardboard cover. Smaller and easier to handle than a whole sheet of stamps, in many countries booklets have become a favored way to purchase stamps.

Coil stamps

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.

This 2-cent coil stamp of the US 1954 Liberty series was used heavily throughout the 1950s and 60s.

A vertical coil pair with a joint line, US 1917