cocoon ID

[TONKA ME]

           Recently found a cocoon under one of my wooden nesting boxes ( I do
wildlife rehab, here in Maine). Never have seen
such a cocoon, so I'm interested in finding out what it is. It is about 1" long
and 3/8" wide with an emerald green hard shell.
It appears to have "gold flake" on the shell as well as a " gold stitch" around
part of the circumference near the top. It may be common, just have never seen
one before. I'm familiar with the birds and mammals here, unfortunately not so
familiar with other creatures. Thanks.
                                      
                                                           tonkame at aol.com