Charlie: Yes the contours of those side sills do look familiar. If so, that would make this a 36-foot car, not 41 ft as I initially stated, rebuilt from NP boxcar series 38300-38999 (Standard Steel Car in 1903
http://research.nprha.org/NP%20Box%20Cars/Box%20Cars%2038300.jpg).

The following photo shows two additional work flats coupled to the original flat car on the same June 1962 date (Evaro, MT):

http://morphotoarchive.org/rvndb/rvndb-zoom-jpgs/RVN26313.jpg

The middle flat shows a different construction, with a deeper, steeply dropping fishbelly portion of the side sill. On other photos the visible details of this construction suggest a structural plate fastened over, or possibly replacing, the original side sills. It looks to be about the same length as the first car. The third car with the A-frame rack resembles the first in side sill shape, but has more closely spaced stake pockets.

Anyone interested can find some scattered diagram sheets for 36, 40, and 41-foot NP company service flats indexed on this page of the nprha web site :
http://research.nprha.org/NP%20Maintenance%20of%20Way%20Equipment/Forms/AllItems.aspx

And some diagram sheets for the original boxcars are at:
http://research.nprha.org/NP%20Box%20Cars/Forms/AllItems.aspx

Chris Frissell
Polson, MT


--- In STMFC@..., Charlie Vlk <cvlk@...> wrote:

The car pictured has a distinctive pressed steel under frame. I don't know NP equipment very well but would guess that the box cars they came from cold be the same ones that were rebuilt into bay window transfer? cabooses.
Charlie Vlk

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