Elden asks

Did these guys come out of Eddystone? If so, it would not be a surprise they chose F30A's.
Those flats were a much better choice than any of the riveted flats, and you often see photos of them overloaded. I suspect the choice was deliberate, as both flats are F30A's.

Elden,

Yes, the locos pictured were Baldwin built S160s. Other S160 builders were ALCo and Lima.

Remember that flat cars, especially during WWII acted as a national pool, However, there would likely have been a higher number available on the home road (PRR) so that helps. Note too that an advantage of the cast frame F30a was reduced light weight, making them capable of taking greater loads. By comparison, the AAR 70 ton flat had a lt wt just under 60,000 lbs leaving only a bit over 150,000 lbs for the load limit, close to a 10,000 lbs difference with the F30A.

That said, other classes of 70 ton flats were used. I have a photo of class Sha (that's the cyrillic letter in front of the number) 93 on a riveted NYC flat. Guess where Sha 93 was built? If you guessed Schenectady, you got it right!

Regards
Bruce Smith
Auburn, AL