Found in western MA on milkweed near the Housatonic River. Much smaller than a monarch chrysalis, perhaps 3/4 of an inch.
CLOSED: Chrysalis ID
My best guess at this point is that it might be one of the tortoiseshells in the genus Aglais - see http://www.silviareiche.com/uploads/8/4/8/9/8489111/2622956_orig.jpg for an example.
Magic Wings Conservatory in So Deerfield MA, tells me it's going to be an Eastern Comma (Polygonia comma.)
They are quite similar - http://www.performance-vision.com/airline2013/sum13-392.jpg
That they are, and I for one could not begin to ferret out the difference to tell one from the other. But what exquisite little containers!