The term triple simply refers to a cover that has three of something. It can be used to describe the number of signatures (a “triple-signed” cover has been signed by three different people) or the number of postmarks (a “triple-postmarked” cover has three different postmarks). It is worth noting that Royal Mail will not postmark a cover more than 2 times, so a triple-postmarked cover will probably feature at least one non-GB postmark. If a cover has more than one postmark, it is usually to commemorate different relevant dates. For example, our triple postmarked Concorde cover (sorry, we have no illustration of BCSP07IOM) has one GB postmark and two postmarks from the Isle of Man. The dates are of the last ever Concorde flight from New York to London (Isle of Man), the last Concorde flight ever (GB) and on the Centenary of Powered Flight (Isle of Man).