board ▁mail ▁post mark , ▁for ▁covers ▁that ▁tra ve led ▁by ▁sur f board . ▁ ▁A ▁colour ▁post mark ▁is ▁on ▁the ▁United ▁States ▁Post al ▁Service - iss ued ▁collect ible ▁en velope ▁comm emor ating ▁the ▁ 2 0 0 4 ▁inaug uration ▁of ▁George ▁W . ▁Bush . ▁ ▁While ▁post marks ▁are ▁applied ▁almost ▁univers ally ▁by ▁or ▁under ▁the ▁authority ▁of ▁the ▁official ▁postal ▁department , ▁service , ▁or ▁authority ▁in ▁the ▁United ▁States ▁it ▁is ▁possible ▁to ▁receive ▁" a ▁permit ▁to ▁apply ▁your ▁own ▁post mark ", ▁called ▁a ▁Mail er ' s ▁Post mark ▁Perm it , ▁and ▁under ▁certain ▁conditions ▁specified ▁by ▁the ▁private ▁express ▁stat utes ▁in ▁the ▁United ▁States , ▁a ▁priv ately ▁carried ▁letter ▁may ▁be ▁cancel led ▁with ▁a ▁private ▁post mark . ▁ ▁Un o fficial ▁entities ▁that ▁issue ▁artist amps ▁may ▁use ▁post mark - like ▁mark ings ▁as ▁well . ▁ ▁Marc oph ily ▁is ▁the ▁study ▁of ▁post marks ▁and ▁there ▁are ▁many ▁published ▁work ▁on ▁post marks ▁covering ▁the ▁topic ▁from ▁before ▁ 1 9 0 0 , ▁such ▁as ▁the ▁fancy ▁can c els , ▁until ▁the ▁present ▁day . ▁These ▁include ▁the ▁so - called ▁fancy ▁can c els ▁of ▁United ▁States ▁to ▁modern ▁machine ▁post marks . ▁ ▁Fe wer ▁post marks ▁are ▁used ▁now ▁than ▁previously , ▁with ▁the ▁advent ▁of ▁meter ▁labels , ▁some ▁types ▁of ▁computer ▁v ended ▁post age , ▁and ▁computer ized ▁post age ▁that