• It looks like a rougher more inked in symbol like the one found in owl cave.  Maybe.   That symbol was triangular/diamond like but was basically a head w ears, same-ish.

google owl cave symbol twin peaks you'll see many images, see if you find it similar?

It's the jade ring owl glyph. 

Its also similar to the the evolved arm. 

Yeah, pretty obviously the symbol in the owl cave and in the ring. Coop says he's looking for that, and we know he's looking for coordinates/locations of the gates to the Lodge. The link seems pretty obvious to me. By the way the fact he uses a card looks like another reference to Windom Earle (take a look at my post in the thread "understanding")

The symbol on the card was the same face the creature in the glass box had.

(it also reminded my girlfriend and me of a heartless from Kingdom Hearts)

For me, it's The Black Dog that runs at night.

The ears also vaguely reminded me of the Joker card.

Does anyone have a screenshot of the card?

Right - I thought he was looking for Dougie.  He had the ring on.  I assumed Doppelganger Coop was going to use Dougie as the switch, so he didn't have to go back to the Lodge.  Dougie fulfilled his purpose ... Good Coop took his spot.

I might be way off.

Here

Owl but much fuller body

Yes, the Owl as depicted on the green ring - and as we've now seen in subsequent episodes, most recently, ep. 11 when Sheriff Frank Truman asks about that symbol on the old map, and Hawk says, "Frank, you don't ever want to know about that."

Is it too far a stretch to think that Audrey's white mask from the original series is the opposite version? Here's the web page banner image at a Twin Peaks blog.

The Little White Mask Blog

It shows up on the map Hawk has and resembles the Bob/egg spewing mother