Help me identify/date an Eames Arm Shell?  

Hello-
I recently purchased an arm shell through Craigslist for a song, and am curious about its age and classification. I know this is a fairly common topic but I'm having trouble coming up with a definitive answer, so I thought I'd submit it here. If there are threads I have missed, I apologize.
The details:
-It's a light cream color -not quite pure white, but not very translucent like the parchment chairs.
- the ONLY imprinted logo on the shell is the Summit double triangles. No HM letters or logo. It does have a paper label with patent numbers and adhesive below that for a longer, skinnier label just below the existing paper label.
-It's narrow mounted, and I do not see the dimples for wide mounts as I have seen on some of my side chairs.
-It's mounted on an H base, zinc colored (ie not black). Seems a bit low for dining height, at least to me. The front is pitched about 2 inches higher than the back.
-The shock mounts have the letters "C" and "N" embossed at 12 o'clock and 6 o'clock, respectively. Not sure if that is of any significance.
-it had strips of dried adhesive along the edges, so I'm thinking this was once upholstered. ETA - there are no screwholes/vent holes in the seat of the shell.
Thanks in advance for any guidance you can give me.