I haven't seen any on scale layouts and I haven't been on the lookout around old train lines outside of town. The search begins...
No doubt it would be a hard score to find. One of the old station shacks in Cripple Creek has graffiti on it from from the early 1900s. I'm hoping some of the old line shacks that have now fallen might have a scratched symbol on it somewhere along the way.
According to my mother, my grandmother, definitely a kind lady, often fed hoboes on the back porch. I wonder where the symbol was and what it looked like. Probably no trace now as this was back in the 30's. Everything looks quite a bit different now.
Probably chalked or carved onto some object nearby, which was associated directly with her home. Mailbox post, fence, utility pole, or even so bold as somewhere near or on the porch.
There were other variations, too, using rocks in various piles and directions. I think three rocks stacked vertically meant "these people expect you to work" or something like that. This was from a book or magazine way back in the mid-60's. My grandparents might well have dealt with folks like these, living within sight of a B&O line.