Back in the 60's, my dad worked for Bendix in Indiana. At some time he visited the site where ECHO was being put together. It was a huge balloon made out of mylar and plated with aluminium on one side and gold on the other. It was launched into orbit and inflated to a very low pressure. It was used to bounce radio signals off of. I remember that he brought a piece back to show me. The point is, I found what I think is the sample. If any one out there thinks they could identify it, I would be glad to send a piece.