dscc7686.jpg

The engine's ID plate, located on one of the engine's mounting brackets. It reads

Rocket Engine

Part Name: Rocket Engine Assy Ascent Lunar Module
Contract No.: NAS9-7498
Part No.: RS000580M
Spec No.: [blank]
Stock No.: [blank]
Serial No.: NONE
Model No.: RS1801C
Accepted: [blank]
Weight: 172
Insp: [some sort of inspection stamp]

Yes, the engine's serial number is the word "NONE".