its a security/acces card, imo.
The question is, what is she reading on it, does it say Walter? Or Billy? Or Shaw?
Then should be asking herself why is Walters security pass on this, if he is with us the whole time?
Or who is Shaw? And does the David android knows something more that he isnt telling.
This scene or still is cleary an assumption fck up, everybody that sees this instantly yell: dogtags!
But when zoomed in it isnt a dogtag. Imo