Got a tricky Eames question!  

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Did you get a look at the mounting points between the frame and back rest shockmounts? I think that would at least tell you whether or not it is Evans.

I found
I found the original Wright auction for the Architonic piece, which lists the date at 52. I do think it's a Miller piece because of the oval mounts instead of the round Evans pieces. But after scouring Wright and Rago Arts I've got almost zero additional information.
I'm going to try to upload images this evening and send an inquiry to Eames Office...see where that gets me.
Maybe someone can help explain what exactly the extra collar does? To me it seems completely redundant - the screw threads into the internal washer in the shockmount, and the head of the screw holds against the leg rod. Why, then, the extra collar?

Repair?
Sometimes these frames break where the bolt hole is...I'd remove the seat and look to see if it has been welded.

Definitely not a repair
This is definitely something done in production. The Architonic piece looks exactly the same as mine. And its on both of the front shockmounts. I can't imagine someone repairing a chair that had twice broken...alto maybe the collar was intended to prevent breakage. Hrmm... still seems awful fussy.

I think
I saw a shell chair with X base recently that also had two sleeves. The sleeves were longer though, about a long as the diameter of the large shockmount.

Rare but not significant
Your DCM is not Evans production, those have the round tabs on the frame at the back shock mount rather than the oval. It is Herman Miller production, early H.M production. 1951 or 52 sounds right. We have a set of Evans DCMs and two sets of H.M. DCMs from 1951 and 1953. The 1953 have the stamped DCM in the seat, and the slip on boot glides. The 1951 have domes of silence, but no embossed stamp and SOME of the set of 6 have the frame reinforcement yours has. I think it was a brief attempt to strengthen a contact point they were concerned about being weak due to the hole drilled in the frame. Obviously it was not a real problem as they quickly abandoned this reinforcement.
I personally don't think that the reinforcement makes it important or significant in the development of the DCM, but the result of the Wright auction may lead you to believe it is.
You may want to take it to a professional restorer to see if the paint can be removed to expose the original dye.
Cool find.

The wright
The Wright auction is also for an aniline red LCM - So I wasnt deluding myself into thinking the chair I have is worth quite as much. I was more interested in the historical significance. It's funny that HM would have been worried about the structural strength of that joint fully 6 years into production. Perhaps they were just correcting what they saw as potential flaws in Evans' production techniques?
Thanks Pegboard and Woody!

Housing Wars
Just curious, Lucifersum. Who won the new home contest, you, Mr. Modernist or your partner, Mr. Traditional? or was it the dreaded "C" word, Compromise?

sweet
Thanks much for all the info about this. I've still got to get some of that paint off to see what the color is underneath. If it's red I may try stripping it down. Or leave it painted. The red that's on now is a beautiful bright cherry red - nice, but a little plastic.
In that the rest of the chair is in almost immaculate shape I still figure I got a good deal.
As to the housing wars...well... my partner doesn't technically own any furniture - so right now the pad is looking very MCM. There was some talk about getting a big oriental carpet for one of the rooms, but even that I can live with, provided its a decent color, and not one of those sickly pale ones. Curtains have been a sticking point and so we have none, lol. We've both agreed to be civil in our commentary of the prez. debate tonight.
Quick breakdown of the rooms:
Kitchen: Eames table, 4 multi Eames side shells, nelson ball clock
Dining room: 2 DCMs and a DCW. RAR as well...mostly just storage room at present.
Guest room: Old oak desk with 1006 navy chair/more storage
Livingroom: Eames lounge, LCW, Risom lounge, DWR couch, anonymous danish side chair, Eames LTR, Aalto stools, Nelson Eye & Sunburst clock, and some 50s bullet planters I picked up.
All the rest of the stuff in the house is Ikea.
I think I'm winning this round 🙂

Another 1952 HM chair with same
Hi -- Just to add to the chorus, I have a 1952 LCM (so, maybe that's a bit different) with the same "reinforced" mounts. And I've seen several others with the same, so it's not a big deal.
And I do recall the auction a few years back when Wright tried to make a big deal of this supposedly "unusual" modification. And it struck me, given R. Wright's vast knowledge of these things, as a bit disingenuous even then. A typical salesman's tactic.

Perhaps
Perhaps it was simply that Wright didn't know. The copy on the auction site seems to categorize this as one of the earlier experiments with shockmounts - like the steel disk mounts. clearly since then its been established that it is later.

Okay,
I'm pretty much convinced it is red aniline underneat. Has anyone has any experience stripping these? My fear would be that whatever agent takes the paint off would take the aniline with it.
So - this is a shout-out to all of the woodworkers out there... what do I do? Paint appears to be acrylic, very thick application, with a white primer. I'll most likely be working indoors, so something less toxic would be helpful if you've got any product recommendations.