This is an extremely interesting locomtive, and is only a few numbers from CB&Q #537.
It is also very similar to D&RGW C-21's #360 and #361.
If you have a chance to view and photograph this engine for detail, it is very well worth your time to do so, regardless of it's condition. Matt Hutson and I used a lot of information gleaned from this engine to document as well as we could #537. Much of this work was featured in the Burlington Bulletin that contained Hol Wagner's excellent history of the engine a couple of years back. I saw and photographed this engine in Campo, CA, following a lead from Bob Richardson in the 80's. A couple of years ago, Mark Valerius helped us out since he lives in the Mt. Pleasant area.