Chris, This has been a great puzzle. I am going to revise my earlier post, and posit that this is D&RG construction during 1881, possibly the main line over Marshall Pass. I've spent some time looking through books and there are photos of early D&RG track constructed with hewn ties, local rock and dirt ballast, and light (30 pound) rail. I found a couple of W. H. Jackson photos which appear to show square jointed track, one very clearly on the main line at Mears Jct.
Thanks for the brain exerciser.
Charlie
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