The most massive structure of the designerInventor of the designer's name was Jaroslav Wanzl, and in 1925 his firm "Merkur" he began production of the very iron design. Production sets and continues to this day. The reason that Soviet industry has set about copying it Mercury, rather than, say, Meccano, is that the Czech designer has been made in accordance with the metric system of measures.
Cc, unfortunately, turned out not entirely successful. When you hold in the hands of the Soviet and Czech parts of sets, the comparison comes to mind Lada and Mercedes. Mercury - colorful metal plates with straight holes, the screws that are not thread breaks, the wheels with rubber tires. There's even a track to make a tractor.