After 30 or so years, the card had become slightly tattered and was covered in plastic to protect it, and in 1996 an article about their correspondence was featured in the then Hawke's Bay Herald Tribune.
It noted that the card was starting to run out of space for the messages that in brief snippets kept each other abreast of what was happening in their lives and families.
Mr Thorne said after that article came out a woman who he did not know read the story and out of the blue sent him a new card, a slightly larger but otherwise exact replica of the original.
"She was going to send it to a police friend in England who was fond of dogs - I would not have a clue who she was, but she sent it to me so we could continue."
From 2000, the men began using the new card, but continued exchanging the original one slipped inside it.
Mr Shaw now lives in Tauranga, and, although they ring each other email to keep in touch throughout the year, the Christmas card tradition is still going strong.
It was Mr Shaw's turn to send the card this year, which caused Mr Thorne to breathe a sigh of relief, as he thought he had it and spent some anxious moments searching around the house for it.
With plenty more space on the new card to keep them going for many years yet, the prospect of a mention in the Guiness Book of Records was tantalising.
"I Googled it the other day and the record for sending Christmas cards was 57 years - by the time we get there though someone else might have it, but we plan to keep going as long as we can."