I recall the first time seeing a U25B upgrade through Cresson, a new look & new sound. The U25's (at least to my hearing) had a distinct sound even compared to other newer GE's. Not only in exhaust "chugging", but also a distinct whine at mid throttle settings.

Many thanks for posting these shots of the Pennsy from the 50's & 60's. It was during this time period that I would go to the tracks every day after school & spend a couple hours watching trains along the main at Cresson, PA. What a variety of power back then, including steam! It was also a real treat to see my favorite steam locomotive, NKP765, pass by that same spot in both directions in August, something i had thought about a number of times but figured the chances of were slim to none.