Frama Stamps or Variable Denomination Stamps
Machine printed stamps, known as Frama stamps (after the name of the company
that invented the vending machines that dispense the stamps), were introduced in
Switzerland in 1976. They are also known as variable denomination stamps and, in German, as ATM's (Automatenmarken - automatic stamps).The Norwegian Post Office is amongst the 38 postal administrations that have adopted the machines. The French Post Office had experimented with a similar system in 1969 and the United States Post Office had introduced Mailomat vending machine meter stamps in 1936.
Baadke, Michael. "Variable-denomination stamps used worldwide." Linn's.com. 1997-2005.
Linn's Stamp News. 2 Oct. 2005. http://www.linns.com/howto/refresher/vending_20000131/
Emmenegger, Jean-Louis. "The Frama Saga." Gibbons Stamp Monthly. September 2005: 48-53.