A genealogy buff found a note addressed to her great great grandfather while sifting through old postcards at an antiques fair.
Ann Waddelow, 68, of Chatteris, Cambs, said she was "amazed" to find the card in Huntingdon at the weekend.
The card had been written to William Waddelow in December 1903.
"I was looking for postcards from Wilburton (Cambs) because I knew my great great grandparents had lived there," she said.
"I found a postcard with a picture of Wilburton church on it for £5.
When I turned it over I was amazed to see my great great grandfather's name and address in Wilburton on the back.
"It was a note from a friend about them meeting for breakfast. It must be a chance in a million; there were hundreds, if not thousands of cards.
Mrs Waddelow, a retired doctor's receptionist who has been researching her family history, said the postcard had come from a collector in York.