Sort of continuing from last week's Sunday Stamps theme of se-tenant stamps, I have chosen one of my favourite first day covers for this week. It's the British Post Office Third Miniature Sheet, issued to commemorate the 1980 International Stamp Exhibition, held in London. This is, in effect, a stamp within a stamp. The inner stamp was 50p, and the outer stamp was 25p which was put towards the cost of running the exhibition.
International Stamp Exhibition, Miniature Sheet, First Day Cover, c.1980