Poster stamps
Poster stamps were used for advertising approximately from around the late 19th century until World War Two. They usually were a little larger than postage stamps but otherwise very similar though without postal stamp value. All kind of companies and businesses used them for advertising on envelopes that were sent by mail and many people were collecting these often very nice and colourful stamps ...
All photos copyright by ©Helmut Janisch/Phonoobsession.
I will add more photos of poster stamps by and by.