a letter mailed within a city at a <#rate=rate> sometimes less than the regular <#firstclass=first class> rate.  Such local letters are of two types: those mailed in cities with <#carserv=carrier service> and those mailed in cities without carrier service.  Some form of local letter rate was in existence from 1863 to 1968.  See also: <#dropletter-gen=Drop Letter>.

gummed labels used by post offices designated as <#exchangeoffice-gen=exchange offices> to distinguish and account for international <#regmail=registered> mail during the period 1883 to 1911.  They are known from at least 25 post offices, with New York being the most common.

a <#revenue=revenue stamp> that is not denominated in money, but in some other measurement, generally a quantity or unit size, for example: one pint, 1/8 barrel, ten cigarettes.  Example: some <#playingcardstam-gen=Playing Cards stamps>.

one of several types of <#grill=grills> used in the 19th century, about 9 x 13mm in size. Example: <#scott=Scott> 92.

a <#uspod=USPOD> service that lasted six weeks in 1960.  It was a “fax” service for inter-agency mail, which the Post Office delivered in specially designed envelopes.