a post office that processes mail in transit.  Also see <#tranmark=Transit Mark>.

<#perf=perforation> holes that are smaller than other perforations holes of the same gauge. For example, <#scott=Scott> 1055 in the <#liberty=Liberty Series> exists with perforation holes of two different sizes (large and small) even though all are perforation gauge 10.  Compare: <#largeholes=Large Holes>.

<#perf=perforation> holes that are larger than other perforations holes of the same gauge.  For example, <#scott=Scott> 1055 in the <#liberty=Liberty Series> exists with perforation holes of two different sizes (large and small) even though all are perforation gauge 10.  Compare: <#smallholes=Small Holes>.

a <#cover=cover> <#frank=franked> with only one <#stamp>.

a <#upu=UPU> <#auxiliarymarkin-gen=auxiliary marking> indicating postage due, typically applied by the Post Office at an <#exchangeoffice-gen=exchange office>.