Tomos started development of its own serial models. In the late 1950s, numerous variants of the moped Puch MS 50 were produced under the common name Colibri. The first Colibris were marked VS 50; later marks ranged from 01 to 013. Individual variants were adapted to foreign markets. In 1959, they produced more than 17,000 Colibris and signed a contract for the first major export to Sweden. Among the most successful Colibris was the type 12, while its version Colibri T 12, which was first presented in 1961 became the most popular moped in Slovenia. In early 1960s, market research showed that the interest in heavy motorcycles was decreasing all over Europe, and Tomos adapted its range of motorcycles and focused exclusively on the production of two-stroke 50 cm3 motorcycles. In order to ensure systematic and organized development, the Institute for Technical and Economic Research was established in 1962. The 1960s were the most productive period for Tomos. The Netherlands emerged as an important market in 1960. Tomos had so much success, that the only other plant outside of Slovenia was built in the Netherlands in 1966. Until 2009 the factory produced for the Dutch market along with research and development of new units. Tomos became the longest surviving moped factory in The Netherlands until production ended in 2009 due to the fact production- and labor costs are lower in Slovenia. The Netherlands remains the strongest market for Tomos today. License production - automobiles Beginning in 1959, Tomos began producing Citroën automobiles under license at the Koper plant, and selling them in the Yugoslav market. The Yugoslav automobile market was closed, so this joint venture with a local firm allowed Citroën to access the market. In 1972 Tomos, Iskra, and Citroën formed a new company, Cimos (Citroën, Iskra, Tomos), for the manufacture and export of cars and car sub-assemblies. Iskra was a manufacturer of automotive components, especially generators. Cimos was half owned by Citroën and half by the Yugoslav government. The Yugoslav government was short of hard currency and often used the barter system, paying Citroën with cereals and raw materials, which Citroën resold in Western Europe. Locally made vehicles included the Ami 8, 2CV6, GS, and Citroën Dyane (called the Diana). Cimos also sold imported vehicles, the CX and Méhari. The Cimos GS can be distinguished by round headlights, developed for the US market but never used there. In