A train passenger left gold worth more than £150,000 in a carriage.
The mystery owner now has five years to claim their fortune, which was found on the train between St Gallen and Lucerne in Switzerland.
In total, more than 3kg of gold was discovered, which has the equivalent value of $191,000 or £152,000. It was found in October last year but today authorities stepped up their bid to trace the owner.
Officials in Lucerne had spent the previous eight months investigating privately but this search proved to be fruitless.
It is unclear though how authorities will verify any claims by parties who come forward to say the gold is theirs.
Last year, a gold hunter claimed to have discovered the UK's largest gold nugget in a Scottish river.
The lump of pure gold, which weighed 121.3g (4.2 oz), was unearthed in a mystery location.
The two pieces form a doughnut shape and could be worth £80,000.
The previous largest find, in 2016, was the 85.7g (3oz) Douglas Nugget.
Speaking at the time, Lee Palmer, a historian and researcher in the field, said: "This is now the largest nugget in existence in the UK. When you look at it, it's doughnut-shaped.
"There are no impurities in it, it is just pure gold nugget of about 22 carats.
"It really is a remarkable find."
