Pipe Gons

Just returned to my side of the pond after a great trip to the Colorado narrow gauge. Really enjoyed Chama and being able to walk around the yard photographing everything especially the preserved freight cars. I was interested to see that the C&TS have a Pipe Gon complete with load and flat cars either end. Can anyone tell me when these cars first came into service and were they deliberately built or converted from ordinary gons?

Must save up for a return trip!

Martyn
PS Ive tried to attached a couple of photo but failed I think it's because I use a mac. Any help there would be appreciated