• Builder: ALCO
• Built 1948, Rebuilt 1967
• RF&P  S-2 # 71

In railroad parlance, this locomotive is a "slug". It has traction motors but no engine or generator. The electric current for the motors is provided by a "mother" unit, a standard locomotive connected by cable connections to feed current to the slug. Without this power source, a slug cannot move by itself and is not therefore a true locomotive.  Normally used in yard and road operations, two or more engines were cabled together by electrical and air controls such that the engineer had complete control over the un-manned unit.  This allowed more freight cars to move at one time with less manpower.

The Richmond, Fredericksburg & Potomac bought 22 S­2 end ­cab switchers from the American Locomotive Company between 1942 and 1948. No. 71 was one of the last batch of 10 delivered in September 1948 (Nos. 62­71). The RF&P then rebuilt three of its S­2s into slugs in late 1967.  No. 62 as "A," No. 70 as "B," and No. 71 as "C."  The RF&P slugs spent their working life switching in Potomac Yard in Alexandria, VA just across the Potomac River from Washington, DC.   The seller acquired No. C in 1983 and have since been using it to provide parts for other ALCO locomotives