dscc5506.jpg

Detail of the engine's ID plate, located on the engine mount.

Picture 2 of 2.

It reads

Rocketdyne
A Division of
North American Aviation
Canoga Park, Calif.
Manufacturers Model	Customers Model
X-A7	X-A7
Manufacturers Serial No.	Customers Serial No.
X001	X001
Type Cert.	Contract No.
[blank]	CNAA-22/ES-RM214
Engine Type	Accepted
G.O. 9577	[inspection stamp]

I'm not certain what to make out of the "X-A7" model designation, with the corresponding serial number of "X001"; presumably, this was some sort of experimental version of the engine.

Additionally, note that the center component of the contract number has "22" overstruck with "ES"; while the other characters are all stamped on a straight line, the "ES" is on a different plane, and the "E" and the "S" do not line up, so I assume that the "ES" was overstruck later.