Originally Posted by Tyger7
 - Elliott’s Mansion COG Tag
Once you arrive, the mansion is attacked. Head to the main mansion area and you will see a large burning flag. On the highest level, to the left of the flag you can find the COG Tag.
This is actually quite missable. After you get done defeating all of the enemies, the chapter ends. You have to get this while fighting.
I missed it : /
Thanks, I've updated the description a little bit.
It's more descriptive and mentions to grab it before killing all the enemies. As far as I remember, the enemies come in waves though, and you can get it in between the waves?