It is one of Britain's most important coin collections - amassed over 50 years by one of the foremost experts in the field.
However, just as Lord Stewartby had begun to create a catalogue of the unique collection, it was taken from his country home in what is suspected to have been a "stolen-to-order" raid.
The array of coins, valued at more than £500,000, features pieces dating back to 1136, when the first Scottish coins were minted, and was stolen from the home of Lord and Lady Stewartby at Broughton in the Borders.
Detectives said they believe the haul had been specifically targeted with a buyer already in place, meaning the collection may never be seen again.
The timing of the raid, while the family was on holiday, indicates those behind it had knowledge about the Stewartbys' movements as well as the location of the coins.
The collection of nearly 2000 includes some of Scotland's oldest-minted coins, including one struck under the reign of Robert the Bruce 900 years ago. Other specimens were created under David II in the 14th century, and James I and James II in the 1400s.
Lord Stewartby is one of the country's foremost numismatists (coin experts) and spent more than 50 years amassing his collection. He was in the process of creating a catalogue which he planned to complete during his retirement.
Lord Stewartby, who is to offer a six-figure reward for information leading to the recovery of the coins, said: "It was a great shock. Although obviously one has a certain sort of pride in possessing interesting old things, my real sadness about this is that it is such a loss of important historical evidence.
"My collection was put together in order to illustrate what was happening in Scotland in the early centuries and I was going to be working on that in my retirement.
Nick Holmes, senior curator of numismatics at National Museums Scotland, said: "The collection is unique and important both for its quality and quantity. This theft really sets back studies in Scottish coinage. It is a total disaster."
"It wouldn't be putting it mildly to say that this theft has put back the study of numismatics back 50 years."
Lothian and Borders Police said the empty home was broken into between Wednesday, June 6 and Thursday, June 7.
A force spokesman said that details were not released until now for "operational reasons".
The spokesman went on: "This collection is a unique part of Scottish history and its loss cannot be underestimated. We are now appealing to the public for help."