Machine postmark

1929 machine cancellation used to cancel 1d stamp on first flight cover from Nassau to Miami

A machine postmark or machine cancellation is a postmark or cancellation on mail that is applied by a mechanical device rather than with the use of a handstamp. Nearly all machine-cancellation devices apply both postmark and cancellation simultaneously. While some mail is cancelled using handstamps, machine cancellation is ubiquitous, and in the industrialized nations the vast majority of mail is cancelled by machine.