Help identifying Eames Rocker Base 60s  

Pic 5 very clearly shows the base to not be original to this chair. The base looks potentially bad in several ways from here.

Thanks Objectworship. What makes you say that?

Impressions from H-base, base marriage, mixed vintages, chrome finish, bad fit, sloppy look...can't say definitively whether base is legitimate depending how you look at it but it's sure not original to the chair here

Any other feedback?

Object is right, the base is a reproduction.
Main giveaways are the mounting tabs that are squared off on both ends (original mounts are rounded on at least one end of each tab) and the screw holes are far larger than in the original design. (Many of the knock-offs depend on larger holes to allow for less consistent measurements that are usually found on the repros. It is simply easier to make the holes larger than it is to manufacture the bases to tighter specifications)
The welds are also sloppy. Welds on original bases are uniform.
The embossed triangle in the shell indicates manufacture by Summit Plastics, Kalamazoo MI. If I am reading the patent numbers correctly, the shell appears to be made in or around 1957, and this is also supported by the Summit embossment. The fact that there is no "Herman Miller" raised letters embossment on the shell also dates the chair to pre 1960.
No clue what the stamped numbers mean.