Question about NYC RS-3s

The fondly remembered fleet of RS-3s that dominated the Harlem Division on the 1950s and 60s all had Alco Builder's plates dated July 1951 (according to a couple of items in an old notebook of mine from that era). However, it's well known that steam operation there continued until September 1952.** Photos suggest that there wasn't much of a steam-to-diesel "phase over" period.This makes me wonder where the RS-3s were used for the 14 month period between July 51 and September 52. Comments?

____________
** With the exception of a few freight jobs like the "Rut Milk" which, according to photos, was using FA's back in 1950.

The RS-3's were the main passenger power into the PC era on the Harlem Line, untill PC bumped the FL-9's into the "new" Metro Region,and off the shoreline to Boston South.
Some did work JN-2 untill all freight ops were moved to PC's NE region,and the invasion of the "black dip" U-23B's took told.

That has no connection with the question originally asked.

NYC had 14 RS-1's. T hey later wound up in Rochester, Syracuse and maybe Buffalo. NYC also had a bunch of RS-2's. Could the new RS-3's have been involved with some shuffling and re-assignment of those units prior to being assigned to the Harlem Division?

The RS-1's and 2's were the diesels that killed steam on the Putnam Branch,and proved the Alco RS concept,The RS-3's were better suited to the longer/heavier Harlem line commuter services and the
longer runs to Chatham,Both the RS-1's and 2's were lighter weight,and used on branches with lightweight rails

Actually, it was the Lima-Hamilton 1200 hp road switchers (NOT Alco RS-1's and RS 2's) that closed the book on steam on the Putnam Division, in 1951. This is an understandable mistake, owing to the look-alike aspect of the LH 1200 to the Alco RS-1. As the Baldwin (BLH) RS-12s were delivered, the LH units were assigned to the B&A, mostly used on the Newton Highlands Branch.

By the mid-1950s the LH and BLH units were withdrawn from passenger service and assigned to the Southern region, where they were well-maintained and rendered service on NYC up to the 1968 PC merger.

Thanks for clarifying that, Paul! It's appreciated.

But so far no responder seems to know where the RS-3s were used between their delivery in July 1951 and their assignment to "kill steam" on the Harlem in September 1952

It looks to me that there was 10 RS3's with a build date of 7-51, NYC 8251-8280. Try looking for photos of these before September 1952.

The White Plains switcher that came down to Woodlawn in the late 60s had an RS. Don't know what model, though.