Now it could fetch about pounds 20,000 when it comes up for auction tomorrow in Mere, Wiltshire.
The bowl was part of a cart-load of "junk" collected during a house clearance in 1973. The buyer, a second-hand furniture dealer, who wishes to remain anonymous, had no idea of the history behind the 13-inch diameter dish and was ready to throw it out before his wife "took a shine to it".
"I was absolutely flabbergasted when I saw it," said Mr Finan. "I recognised it immediately as a fine example of an Hawaiian pakaka, which are worth up to pounds 5,000 anyway. I found out that it had come from a clearance sale at Bridwell House in Uffculme, which at one time held a large number of Cook artefacts that were sold for auction in 1967. This piece was obviously overlooked, among all the whale ribs, coral and furniture."
The owner said: "I cannot believe that we sat staring at this valuable antique for all those years."
Collectors from Europe and America and representatives from the British Museum will be among the bidders.
Mr Finan added: "We have this man's wife to thank for inadvertently preserving this historic piece. There is a huge amount of interest in Cook's artefacts."