How to identify iPhones in Photos

In Photos you may create smart albums by different criteria. One of them is the type of camera, i.e. Canon, Olympus, Nikon etc. and the different iPhones.

I used to have an iPhone 4 S, and it was easy to distinguish that from my wife's 6S, but now both my wife and I have an iPhone 6S, and I can't figure out how to create a smart album showing i.e. only photos taken with her iPhone.

Is there any way to distinguish between the two iPhone 6S's?

Actually the reason why I want to distinguish is that her clock is behind my iPhone clock, and I want to adjust the time of her photos. This is easily done in Photos if only it is possible to distinguish between the to iPhones.