Rocker- RXR / RAR

One of the more intriguing chairs in the JF Chen Eames Collection 
is this Zenith rope edge "RXR" chair. 
Image Source: Eames Designs

The rocker base seems to be somewhat of a mystery.
The idea is that it's some sort of pre-production rocker base prototype. 

The facts: 
Produced by Zenith, so that dates it at, or after, 1950 
Labeled DAX, with wood (looks like stained ash) runners attached.
I saw it up close and the screws have screwdriver marks.
The runners, base and shell seem to be in mint condition

In 1948 MoMA held an "International Competition for Low-Cost Furniture Design"

Eames Office teamed up with the UCLA School of Engineering and produced these designs. 
The Eames designs tied for second place in the competition.  
Don Knorr won first place in seating for his enamel chair for Knoll.

A close-up view from the 1948 MoMA competition

MoMA owns the 1948 full-scale model from the competition shown here.

Neoprene-coated aluminum shell, metal rods, and wood runners.
The front the legs mount from the top like the JF Chen "RXR",
 but the rear ones mounts more like the production base. 
Image Source: MoMA

Early mock up prior to fiberglass production, but after the 1948 version.
The legs attach to the runners on the inside like the production model. 

Eames Plastic Chairs, Herman Miller brochure

1950 first production RAR with the early discontinued wire frame configuration.
Image Source: Eames Designs

Eats on prototypes at the Eames Office
Image Source: Life Magazine