Making HK$138,000 in a museum gift shop
When visiting the museum of the Hong Kong Monetary Authority, electrical engineer Chung To Kong came across a souvenir paperweight that was filled with shredded banknotes. The paperweight claimed to contain 138 shredded HK$1,000 banknotes. The total value of the banknotes in the paperweight was thus HK$138,000 or some $17,600.
Paperweight with shredded banknotes sold at the museum of the HK Monetary Authority
Source: Kong (2024)
Needless to say, the paperweight was not sold for HK$138,000 presenting a significant arbitrage opportunity. If one could reassemble the shredded banknotes, one could make a fortune.
Being an electrical engineer, Kong set out to prove that using computer vision one can indeed – at least in theory – reassemble the shredded banknotes in the paperweight. The pictures below show three examples of shreds and where they fit on a Hong Kong banknote.
Positions of shredded banknote pieces on a real banknote
Source: Kong (2024)
It’s a nice way to finance your tuition fees if you can do it. Unfortunately, Kong discovered that not all paperweights seemed to contain 138 banknotes. While two of the paperweights bought seemed indeed to be made of 138 shredded banknotes, another one seems to have contained only 82 banknotes plus five small stones.
Kong wryly remarks that the Trade Description Ordinance in Hong Kong states that it is illegal to make false, misleading, or incomplete descriptions of the content or merchandise. He concluded that the Hong Kong Monetary Authority seems to have broken the law.
PS: The paperweight gifts are no longer available in the museum gift shop. It is unknown why they have been withdrawn.
16,000 bags full of shredded Stasi documents are slowly being addressed in a similar fashion https://hackaday.com/2023/06/12/spy-tech-unshredding-documents/ , but it's been slow going: "To help, the German government turned to computers and the Fraunhofer Institute. Scientists there demonstrated software known as e-Puzzler that would revolutionize the document reconstruction process. However, that turned out not to be the case. While it does work, the process is painfully slow. ... The Fraunhofer system did help Bundesbank match up damaged banknotes. However, banknotes are more uniform and have known features that the Stasi documents lack. And, as you can see in the video below, it still looks like there is some manual work required. Despite putting in about 6.5 million euros, the official word is the process didn’t scale well for this many documents."
Some weekend reading on the technology emoloyed https://d-nb.info/1237622654/34 .