The metal object between the rails is a RibbonRail gauge:
The abutments I made previously turned out to be too narrow for the approach fills. For the shorter abutment on the right-hand end, I was able to remove the top course from the taller abutment to substitute for the smaller one, but I then had to recast the larger (left-hand) one. The original larger casting was repurposed (upside-down) as a retaining wall, which is visible below the transfer crane in the last photo of the November 29 post.