I grew up in Lewistown, PA and PRR based an MOW/Wreck train out of the Lewistown Junction yard. All of the equipment in that train was painted yellow; same as Norm mentions for the one out near him.
i don't know when PRR started painting MOW equipment yellow but, it was that way in the late 40's/early 50's. The photo appears to date from the 1920's and PRR may well have used Tuscan for MOW equipment at that time. I have to agree these do look like MOW bunk cars despite the (to me) odd color.
Huntingdon was my Dad's hometown and I was never aware of a silk mill there. After seeing the photo in the OP; I Googled the name and it turns out this plant is what I knew as Owens Corning in the 50's and 60's. The plant still appears to be active under another name and produces fiberglass products.
Anyhow; a neat old photo! Thank you for posting!
Curt