375 main rods...

Just curious, 375 seems to have had the squared main rods early in her life. some time after the flying Rio Grande was applied, new "round" main rods were added.

Here are a few links to pics:

(Denver Public Library) 375 in the thirties with the "square rods"

[cdm16079.contentdm.oclc.org]

(Denver Public Library) 375 in the forties with square rods:

[cdm16079.contentdm.oclc.org]

(Dorman Collection) Durango Switcher with round main rods:

[ngtrainpics.photoshelter.com]

From my very limited research, it seems the round rods were added in Durango while she was the switcher. Is this the case? Does anyone know the story behind this?

As a refresher, what were the years that 375 was used as a switcher in Durango?

Casey Akin