DPS Engine Mockup

In the lobby of the "old" museum building (where the ticketing counters and gift shops were located) are two lunar module engine mockups, a Descent Propulsion System (DPS) engine mockup and an Ascent Propulsion System (APS) engine mockup. Both are constructed of what appears to be sheet metal and seem hollow (perhaps double-walled?).

This mockup is displayed without its nozzle extension so it's harder to directly compare to a flight engine, but it would appear that the DPS engine underwent a number of design changes between this mockup and the final flight configuration in its valves and plumbing, gimbal ring, and overall shape.