I do not have a PRR Timetable to check/verify the PRR Milepost 115.32.
Monon Timetable #8 (Effective October 25, 1956) and others in the same time period show:
The Following crossings are protected by semaphore target and gates:
Monon.............Monon
Frankfort .........Penna.
Midland............C. M. St. P. & P.
Elsewhere with the various descriptions of individual crossings it has:
"At Frankfort --- Penna. Crossing: Gate open and signal diagonal, crossing clear for Monon."
The signal and gate in the picture appear to be set against the Monon. The gate is almost hidden in the roof line of the building across the tracks.