The 2344 New York Central F3 B unit of the early and mid-1950s was produced to be used with either the 2344 or 2354 NYC F3 AA diesel. When a 2344C is coupled between a pair of AA diesels, the end result of an impressive-looking ABA unit. The ABA lash-up was both prototypical and a common sight on US railroads during the 1950s and 1960s.
Externally, the 2344C followed the same manufacturing change as the 2344 and 2354. From 1950 thru 1952, the 2344C had wire-cloth roof ventilators -- exactly as those found on the the 2344 F3 AA diesels. For its final three years of production (1953 through 1955), the 2344C had plastic ventilators molded into the body -- just as the 2354 diesel was manufactured. Therefore, if you are looking to match a NYC B unit to an AA diesel combination, there is an early and late version of the 2344C. To this day it remains a mystery as to why Lionel changed the number of the AA unit regarding the ventilator change but not the number of the B unit!