In the early 50s Rokus comes into contact with Sio. The Sio collection at that moment consists of a random collection of products.
From the beginning Rokus and Corry standardize and create links between their products. They are soon responsible for everything. They design the packaging, catalogues, manuals, logos, stationery, advertisements in magazines and newspapers.
Further, they design display windows in department stores and sales stands of the Annual International Toy Fair in Nuremberg.
In this all, the photography of brother Piet Mobach was always very important.
Rokus and Corry have everything in hand, from initial design to implementation, always taking into account the possibilities of the technology. When printing, the process is continuously monitored often by being there, stimulating the printers at work to get the best possible product.
In the design of toys Rokus and Corry create high pressure to get often to the limits of the available techniques. Regularly in consultation with Rokus, Sio purchases new machines in order to further improve of the quality.
This all ensures a consistent design in all areas within Sio, years before design managers name this as corporate design.
Rokus and Corry determined everything from the first design to the production for decades. However, after director Mertens stopped in 1977, that changed quite quickly. Sio Amsterdam saw a number of directors come and go in a short period of time. Calculations and product managers who had no connection to toys were in charge. This was characteristic of the company's relationships at that time. In 1981 the logo designed by Rokus and Corry, with the three Sio letters, was changed behind their backs to a pink square with the letters below it. This logo ended up on many products that Rokus and Corry had designed, but it no longer felt like their design.