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The sign on the side of the pedestal on which the engine rests. It reads

Lunar Module Ascent Engine

This is an engineering model of the 3,500-pound thrust ascent engine. The engine was not gimbaled and it performed at full thrust. The engine remained dormant until after the ascent stage separated from the descent stage. The propellants used were helium-pressurized Aerozine 50 and nitrogen tetroxide.

Technically, of course, the ascent engine remained dormant until just before the ascent stage separated from the descent stage, because it was the firing of the ascent engine which effected the separation :-)