Originally founded in 1959 this factory was set up by the Dutch government and was meant to increase the social integration of disabled people by making it easier for them to get a job.
From 1962 onwards the models (most of them, but not all, in 1/64) were sold under the Best-Box name, but around 1971 the company name was changed to Efsi. This probably originates from the organisation that was behind Best-Box, FSI (Federation for Social Integration). It was also around that time that a wide range of truck models of various brands started to appear on the market.
Manufacturing promotional models became a major part of Efsi's activities during the 1980's and 1990's, and the quality of the models was further improved by replacing the 'fast-wheels' with less toy-like wheels with rims and better decorations. Efsi also supplied models to Siekmann & Co. in Germany that offered the models with their own printing under the ASA2000 name until 1986. The Efsi name itself was used until 1988, at that time the FSI seized to exist and the factory closed its doors. The moulds were sold taken over by Holland-Oto.
What's it worth? Take a look at this Efsi price guide: sold listings for a value indication.