Chris,
Thanks for the interesting puzzler. I still have not found the exact same image you cropped from, but I have found a number of D&RG images from the 1880 - 1883 period showing this feature - square joints on the new D&RG track. This includes several on the Marshall Pass line, including a couple at Mears Jct, one of which very clearly shows the square joints on the main line. Another, titled "Cascade Near Silverton" shows the track with sawn ties, but square joints. The view looking toward Hamilton Point, titled "First View of the Chama Valley" also shows square joints, but on hewn ties, similar to your sample image.
I think we can now say there seems to have been a practice of square joints early in the D&RG life.
I looked at a couple of Jackson images of the new, temporary narrow gauge (on standard gauge ties) between Minturn and Glenwood Springs, and these seem to show staggered rail joints.
Very interesting!
CVM
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