In checking why Jamaica in the file name: I found out the car "JAMAICA" is the second car in the photo! Interesting lash-up. Further info: Pullman heavyweight QUEEN MARY built in 5/23/1925 for the Lehigh Valley. In 1945 it was sold to the Wabash, which points to an assignment in a Detroit - Chicago train. The PRR ran these with the Wabash 11/12/46. In 1950 ithe Wabash sold it to the PRR. 3/15/1949 It was withdrawn fro Pullman lease in October, 1956.
As the FM-H16-44 no.1504 is pre-Dashing Dan I labeled it c.1958
Yes, it looks to be the stretch between East Patchogue and Yaphank where the Montauk is parallel to the LIRR