Siku is a range of scale model vehicles produced by a German company called the Sieper company. The Sieper company produces a wide array of vehicular models in a wide range of scales including the 1:32 farm models which I regularly use in my conversions. They also owns Wiking-Modellbau which produces the highly detailed Wiking 1:32 scale farm models.
The Siku Farmer Series of 1:32 scale farm related models was introduced in 1983 and the Farmer Classic series of vintage models was introduced in 2002. The Siku Control 32 model are a range of radio controlled 1:32 scale models, mostly tractors but with a few lorry models also. In 2004 the first Siku Control 32 vehicle was released, a Infra-red controlled Fendt 930 Siku number 6754 and they have continued to gain popularity ever since.