There are two IDplates on the exterior of the combustion
chamber.
This represents the center engine (which was not designed to gimbal), so
its gimbal
outriggers attach to fixed struts.
This is a later engine, as indicated by the presence of studs and
nutplates used to mount the engine's thermal insulation on the
outer surface of the engine.
Time picture taken
Sat Jun 25 11:39:52 2011
Location picture taken
Apollo to the Moon Gallery
National Air and Space Museum
Washington, DC