Unlike the LEGO sets of today, The mid 1950's and 1960's LEGO sets were originally designed to be more of an architectural toy. The bricks themselves were used to build scale buildings and they were accompanied by ~1:87 scale plastics vehicles with metal wheels (I call them micro-vehicles). I don't believe these vehicles, at least not all of them, were ever offered in the United States, since Samsonite first introduced LEGO here in the late 1960's and early 1970's. LEGO then opened their US shop in Enfield, CT in 1973.
I'm in the process of photographing them and detailing the different color schemes for reference. In addition, I have a some catalog scans of that era. If you have any of these type of sets, especially any not listed, please help me to compile a complete list of set numbers for everyone to reference.
Many thanks to Gerald Cohen and Guy Blanpain for their assistance in helping me to compile this list and acquire both photographs and catalog scans.
Current endeavors include researching the cost to have both replacement decals and replacement headlights fabricated for the micro-vehicles. Truck Decals and car headlights are the most common missing elements of these sets. IF YOU ARE INTERESTED IN EITHER, PLEASE SEND ME AN E-MAIL AND I WILL NOTIFY YOU OF THEIR AVAILABILITY AND COST.
This site, hyperlinks and the information contained in this reference are not nearly complete or 100% accurate - it is merely a beginning.