what is this rectangular icon in my Nexus 5x notification area?

[AC Question]

I have an icon I've never seen before in my Nexus 5x, looks like a taller than wide rectangle with two lines on each side of it. I've never seen that before. I tried to find it and it might be an image carousel icon but I have no idea what that indicates. Any clues how to look this up? I can't attache it or paste it here so I uploaded it to dropbox.
www.dropbox.com/s/z2zogojzfmp0yk4/icon.jpg?dl=0
TIA,
Mike

 

[hallux]

Your phone is in silent/vibrate mode.

FYI, if you sign up (it's FREE), you can attach images and after 10 posts you can post links.