Gray market refers to machines that were manufactured to not be sold by new machine dealers in the North American markets. In addition to Caterpillar the manufacturers that did this include Hitachi, Komatsu, Kobelco and others. In my experience Cat machines were some of the later imports in the gray markets. All the Cat dozers below a D6 as I recall came from Japan and the only real difference is that Cat dealers usually would not look up parts for if it was "gray." If you found a comparable machine serial number for a North American model you had no problem with parts.
The first grays that I had experience with were Hitachi excavators.
Most of the gray excavators had some big differences between North American and World Wide machines. Cat excavators in particular had different cab enclosures and maybe some different option packages. Komatsu had different size boom cylinders on their excavators. I worked on Dash 5 excavators that had no electronics and others that had electronic hand controls and some ability to learn operational functions. All could have come with pattern control changer manifolds but many did not. I worked on Hitachi excavators that had air conditioning systems and no heaters.
So much of what is sold today is only here as a result of the gray market. Hand control pattern changers, zero tail swing excavators, depth control, swing booms and rubber band tracks were all proven in the market by machines brought to North America outside of the franchise dealers.
