Many generations of Czech children have dreamt of finding this item underneath their Christmas tree. It was true for decades that when you said the word Merkur to a child in this country the first thing they thought of was not the planet Mercury, nor the Roman god, but a metal construction set, similar to the British Meccano or the American Erector Set.
Models constructed from Merkur - be they miniature cranes, cars or tractors, can still be found in many households even now, as their owners were sorry to ever disassemble them. But more than that, Merkur was present at the birth of one of the best-known inventions by a Czech - the soft contact lens. After more than eight decades, Merkur is still here today and will be found underneath many Christmas trees this year.
This year, a museum documenting the history of the construction kit was opened in the town of Police nad Metuji where the toy is also manufactured. Radko Kriz, himself a proud owner of a Merkur set as a little boy, is in charge of the museum.
"The history began in 1920 when Mr Jaroslav Vancl founded the company Inventor, Ltd., in Police nad Metuji. It first manufactured a construction kit called Inventor, a predecessor to Merkur. In 1925, Mr Vancl came up with the idea to manufacture Merkur as we know it today."
The first version called Inventor used hooks instead of screws, making the pieces difficult to assemble.
"Inventor used a system of hooks - the same mechanism is used to this day with some types of scaffolding. The metal beams had hooks at the ends, which you connected to holes. It was difficult and that was one of the reasons why in 1925 Mr Vancl opted for screws, nuts and bolts, giving birth to Merkur."
We will probably never know to what extent Jaroslav Vancl was inspired by similar toys already marketed in the West, but abandoning the old Inventor version paid off. Radko Kriz.
"That proved a fortunate step because Merkur provided great versatility and a great variety of combinations. That's one the reasons why there is still such a demand for Merkur. In the beginning, Mr Vancl produced a very simple set, with only 30 parts but in a few years' time he came up with new kits, new packaging, new construction possibilities. Merkur kept on improving, even in the communist era. Nowadays Merkur consists of around 250 different parts."
A boom came in the 1930s when new parts were added including simple electrical appliances. Also, the company started manufacturing electric toy trains. But, like almost everything else, the development of Merkur was affected by the Second World War.
"Production was reduced during the Second World War when there was a general lack of metals. Another critical moment was nationalisation after 1948 but Merkur survived that as well. The factory was swallowed by the state company Kovopodnik but Mr Vancl was still allowed to work there."
It is a paradox that the most difficult times for Merkur came after the fall of communism. Radko Kriz continues.
"The most critical period came after 1989. The factory was not returned to the heirs of Mr Vancl but was privatised. But the company that acquired it soon went bankrupt. Production was interrupted for some two years. That was the worst time for Merkur. Two contenders appeared then: my father who had been involved in the metal business and a rival company, Meccano, which wanted to buy Merkur to get rid of competition in Eastern Europe. But they did not succeed and Merkur is now successfully developing."
Even though similar toys existed elsewhere, Merkur still made it beyond Czechoslovakia's borders.
"Merkur is a phenomenon, not only in the Czech Republic and Slovakia. The founder of the company, Mr Vancl himself took part in the Chicago World's Fair in the 1930s. Merkur was exported mainly to the Soviet Union. Often it was not available in this country because everything was exported in order to get foreign currency. Today we export into the EU and also to the United States, Canada, the Russian Federation and former Soviet countries."
One of the most important moments for Merkur was when the inventor of the soft contact lens, Professor Otto Wichterle, used it in 1961 to construct his "cockostroj" or "lens machine" to make the first pair of contact lenses.
"Of course, Professor Otto Wichterle made his first contact lenses on a machine made from Merkur. It was on Christmas Eve and he had nothing else about the house but Merkur. Using a small dynamo and a small motor he built this primitive machine and produced the lenses. The original machine is at the National Technical Museum. In our museum, too, we devote some space to Mr Wichterle."
The museum, located in the town of Police nad Metuji, was opened earlier this year and apart from the history of the construction set, it also displays artefacts made from it.
"Above all, it is the largest construction made from Merkur by Jiri Mladek. It is called 'Ocelove mesto' - 'The Steel City' - the Czech translation of Jules Verne's novel 'The Begum's Millions'. We look at the complete history of Inventor and Merkur, the boom of the 1930s, the era of socialism and current production. We also have the electric toy trains that not everybody knows Merkur used to produce. Production was discontinued in the 1960s but we decided to renew the production last year and visitors can now see the new trains in our museum."
And finally I asked Radko Kriz whether he believes Merkur is still interesting to today's children used to all kinds of sophisticated electronic toys.
"Today competition is tough. Children have many more options how to spend their free time than 100 or 50 years ago. But Merkur has a place among the toys, especially for manual skills, because no computer, no virtual reality can replace it. It is necessary to return to reality once in a while and try and make something with your own hands with a screwdriver. And Merkur is an ideal tool for that. And that's why there is still demand."
Since it opened earlier this year, more than 20 percent of all visitors the museum of Merkur has welcomed, came from abroad. Mostly from Poland but also the Netherlands, Germany, the United States, Canada, Mexico, New Zealand and Australia.
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