Question about an Eames aluminum group chair  

This is my first post. Thanks for any help!
The chair is a Herman Miller Eames aluminum group chair marked "patent pending".
My question is "Does anyone know why someone would grind down the metal on one section of the outside frame where that section meets the yoke." Sorry if I'm using any incorrect terminology. Please see picture.
By the way, it's hard to tell from the picture, but there is plenty of clearance for the yoke where it meets the frame, without the grinding.
Everyone I've talked to thinks it might have be re-upholstered or disassembled, and someone had a hard time getting the pieces back together.
This sounds reasonable, but the frame is in such good shape that I think it is possible that it hasn't been re-upholstered. Also, it looks like where the tag hangs down from the cushion over the yoke has protected that particular part of the polished aluminum finish for a long time. The finish looks almost brand new in that area. You might be able to see it in the picture.
To make a long story short, why would anybody grind down part of the aluminum frame on an Eames chair?
Thanks for your help!
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