The 6500 series I beleive were built first.
Followed by 6200 and 6300 cars.
I dont have my photos on me to be perfectly descriptive of each, however...
Both were made from STd gauge cars. One was I beleive an outside braced box car similar to the std gauge cut down pipe gons, they have steel sides and underframes ofcourse and lots of holes on the sides showing eviedence of the rivet holes from the outside bracing.
The other car type I beleive has steel plates on the sides for bracing with loops welded on for stake pockets. I belive they were steel reinforced wood cars.
There were multipule cars of each type sittin on the siding east of Cumbres pass that I walked up to and photoed a couple years ago. Im sure there are lots of both types on the C&TS.
I will look for my pics.