It was an Overland On3 C&S number 72, it has already sold for $ 1,176.51.
However, there is an Overland On3 C&S number 73, from the same late 1980s Overland run, currently listed at BrassTrains.com:
https://brasstrains.com/Classic/Product/Detail/085622/On3-Brass-Model-OMI-0113-C-S-Colorado-Southern-2-8-0-1986-Run-Unpainted-EXACT-MODEL-UNKNOWN-It is priced at $ 1,295.00 with free shipping.
Lots of great photos of the model to see what this rare run of On3 C&S locomotives looked like.
Jim Courtney
Poulsbo, WA