Keith,
as far as I can determine; the Scalehouse was at the American Smelting Works, not the Arkansas Valley Smelter,

note position of the chimney, these are polar views; the upper looking East towards Leadville.

However there was a similar single-window version at the Arkansas Valley Sampler, that out lived the operation at the Penrose.

This had begun life as a single-doorway shed(found in very early Jackson images) and enlarged. There is nothing to suggest this version was over tracks at anytime and isn't the version in the montage above.
UpSideDownC
in New Zealand