John

If you are referring to the gasoline version and diesel version there were two series. As you know these were built by David Brown and was imported from 1960-63. The tractor was first distributed from the Cleveland plant and later from Charles City plant. My cousin was a dealer during this time and he sold several. They were tough in 30 hp tractors but hydraulics gave a little problem. 
As for the gentlemens question as to the worth, I saw one sell that was sold new in 63 and had been used as the only tractor by the farmer. It was a diesel, straight tin and good tires. It sold for $1550.