A man from Morecambe believes his dog has found a rare piece of whale vomit while walking on the beach.
Ken Wilman said when Madge the dog "started poking at a rather large stone" he realised it was unusual.
He left the ambergris on the beach but "something triggered in my mind" and, after doing some research, he went back to get it.
The substance, which is found in the digestive system of sperm whales, is valuable and used in perfume.
Mr Wilman said: "When I picked it up and smelled it I put it back down again and I thought 'urgh'.
"It has a musky smell, but the more you smell it the nicer the smell becomes."
He is now waiting to get the 3kg (7lb) piece tested and said he had been offered 50,000 euros (£43,000) for it by a French dealer.
Andrew Kitchener, principal curator of vertebrates at the National Museum of Scotland, said: "It's worth so much because of its particular properties.
"It's a very important base for perfumes and it's hard to find any artificial substitute for it.
"Over time it becomes a much sweeter smell as it oxidises, but initially it doesn't smell very nice."
Ambergris is a natural excrement thought to be used by the whale as a digestion aid and is expelled from its abdomen often while hundreds of miles away from land.
The hard beaks of giant squid, a main source of food for sperm whales, have often been found inside lumps of ambergris.
Initially, it is a soft, foul-smelling matter that floats on the ocean but through exposure to the sun and the salt water over years it turns into a smooth lump of compact rock which feels waxy and has a sweet smell.
It is still used in perfumes, although many perfume makers now use a synthetic version.