I've seen them only once on the envelopes coming from Germany. If there is anyone knows more about them
(release date and purpose of use) let me to know or leave a comment.
Year: ?, Self-adhesive, Günter Mair's catalogue no: - FRG-A-?, imperforated, sheets of 10(1x10),
glossy, bright dark blue/dark red/white, ref.: 912-687-000.