My cta model Trains 6000 series o scale.

What are they made from?

Looks like some kind of paper / cardstock --ie: something from one of the books you cut along the dotted lines, fold, etc.  -- looks like pre-printed smooth cardstock materials.  The cars and the "track" and "structure"  !!  I have seen those type of model "kits" at times.   Here are the N SCALE paper Models of CTA trains you can assemble --- here is their website link

http://www.buildyourownchicago.com/trains.html

I just checked - I was correct --- see additional update -- here is a post about these paper models he made back in August 2017 in the S SCALE forum... link to thread below:

https://ogrforum.com/...22#74213916804892522

Regards - Joe F