See the classic thread by Derrell Poole titled
"Eight-wheel Caboose on the C&Sng" (
http://c-sng-discussion-forum.41377.n7.nabble.com/Eight-wheel-Caboose-on-C-amp-Sng-td488i100.html)
At the bottom of page 6 of the thread (April 6-8, 2015) there is a long discussion on the caboose folios, when they might have be drawn, and if any conclusions can be drawn as to what they mean relative to a specific era.
Jim
Jim Courtney
Poulsbo, WA