Michael Amphlett bought the single-malt bottle dated 1937 as a present for his dad in 1978, in Fort William in Scotland.
But his father died from prostate cancer in 1991, so Mr Amphlett Snr never got around to opening the bottle of whisky.
The bottle sat forgotten about in the back of a cupboard at Michael's mother's home, until she too passed away in 2016.
And now, the 82-year-old bottle of whisky has fetched £2,700 at auction last month - more than 200 times what Michael paid for it 42 years ago.
Michael, from Cholsey, Oxon., said: "I seem to remember paying somewhere around 10 or 11 pounds for it.
"I didn't really know much about whisky, let alone single-malts, but the guy in the shop advised that it was a very good whisky.
"However, it was the 1937 year date on the neck label which caught my attention.
Picture: SWNS
"That was the year my father came up from Westbury in Wiltshire, as a 19-year-old, to work in the Bolton Bros glove factory in Didcot.''
His father was pleased with the present, but he decided not to drink the whisky until 1987 when it would have been 50 years old. But when 1987 came, he decided to wait a little longer to open the bottle.
Michael's father died four years later from prostate cancer, in 1991, and he never got to taste the contents of the bottle with his son. The whisky bottle then went back into the cupboard for another decade.
Michael said: "The bottle stayed in my mum's cupboard for ten or more years, and significantly, by then, I was just getting into single-malt whiskies.
"My favourite had become Macallan, so I was staggered to find that, when I rediscovered the bottle, it too was a Macallan as, in the ensuing years, I'd completely forgotten what it was."
His mother later died in 2016 and after clearing out his mother's house the whisky bottle was taken into his care.
He added: "I knew it was going to be worth something, possibly a four-figure sum, but it wasn't until I enquired via the Whisky.Auction website how valuable."
Michael said he could not bring himself to drink the whisky without his father and, after finding out it could be worth something, he decided to put the bottle up for auction.
It was his first auction, as he said he had never owned anything so intrinsically valuable before.
Michael did as he was advised and set a reserve of £1,750, which was raised on January 12.
Then it climbed to £2,100 on the 18th and again on the 21st from £2,200 to £2,700, which was the final hammer and the winning bid.
When the bottle of single-malt whisky was sold at the auction it was 82-years-old and had been owned by Michael for 42 years.
He said: "I had no idea that whiskies of that type could be so expensive. I just happened to be the right age at the right time."
He added: "I have to say I was both surprised and very pleased, but tinged with a little sadness that my dad didn't get to taste it with me.
"But, if he was still here, I do believe he would have had a wry smile on his face."
