Cast iron numbered marker of some kind?

I bought this cast iron numbered marker of some kind on Ebay a few weeks ago. It's 10 1/2" wide by 8" tall,on the backside are 2 ears with holes that protrude upwards at a angle 2" above the top if looking at the front side. The number 23 is raised,painted silver and the rest of the plate is painted a flat black. On the back side there is a letter c about 7/8" tall near the center. The back is caked and flaking with a coal like residue and smells like coal.

Anyhow i bought this because the seller thought it was a RR mile marker of some kind and she also lived in Colorado. I asked her if she could send me a note with a little history about it when she mailed it to me. Here's what her note said: I can't be 100% sure,but these RR markers are from a Colorado line. they were found in my grandfathers barn in Florence,Colorado. He lived right beside a RR there. He was a coal miner all his life. The seller also said she had one more of these markers with a number 2 or 3 on it.

I'm not familiar with any cast iron western RR milemarkers, or signal pole number plates. Sooooo does anyone on here have any idea what this might be off of or where it might have been used if it came off a RR line around Florence Colorado? The woman also had a D&RG marked spike puller bar listed on Ebay wich came from her grandfathers barn. For all i know maybe this numberplate is instead something from a pc. of coal mine equipment or mine in Colorado?

Thank's for any input on this!