How to identify moble phones?

My wife and I have identical Android phone.  When I import photos from the phones -- which is a pain -- the images from both phones have the same Make and Model in the EXIF metadata and the Serial Number is blank.  This makes it impossible to tell which photos are from which phone.

As a workaround, I need to set a keyword after or during import.  If I forget, there is no going back.

Is there a way that I am missing to tell which images came from which phone?

Thanks.