Maybe, Eames being a Brit who grew up in the eighties, he's using the probably-a-wallet-chain to signal sexual preference [left = top, right = bottom, if I recall -- can't find any supporting evidence via google!] as well as to deter pickpockets.

And thank you for all of this post, especially the parts that point out how non-vile, non-shabby Mr Eames' wardrobe is! (I especially like that salmon shirt. It's very Africa and very distinctive. Silk, maybe?)