B'day from Kate - A Brain Twister

Double Marilyn's from Kate. I like her arrangement and spacing. I can't figure out what that very faint shadow is. It must be whatever she put in the envelope to give it a little more body to withstand the postal machinery. At first I thought it was a shadow created by the general dust and whatever rubbing up against the envelope as it traveled through the machines - but was in the shape of the paper inside. That gave me an idea that I love-love-love -- to put some shape in the envelope and do a rubbing. How can I remember this idea? Does anyone else like the idea?

That's really nice gold. I wonder what it is? Will Kate remember and also let us know?

***

This is mostly for my BigHelpfulBrother - who has been out of town so he probably isn't in any kind of mood to work on a puzzle. But, it's such a good puzzle. I thought of it all by myself - although that doesn't mean anything. It might be something that I've seen before but The Big Thud deleted the part where I knew I had picked it up somewhere.

Here it is. A series of numbers - not in numerical order. So why are they in that order?

It is not random. There is a method. What is it?

8549176320

Feel free to submit your guesses.

I know there are a couple other readers who like numbers and puzzles.

Also - how long it took to come up with the answer - in case more than one of you figure it out.

OK -- he figured it out really fast

and the answer is in the comment he left.

Congrats.