Just like Gmail, Google Photos relies more heavily on search than a traditional folder system to organise photos, and there are a number of useful operators that can help you sift through your pictures in seconds. You can identify images based on location, subject, people, and even by camera type.
We first saw the tip in this post on the always informative Google Operating System blog, and we've had luck searching for #sony, #nexus6, #iphone and #canon in our own Google Photos account. We don't have the broadest sample of photos to test this with, but if you play around with different hashtags you should find something that sticks -- essentially you need to type the camera model as a single word with a hashtag in front of it.
It's another way of quickly sifting through your pictures in seconds with nothing more than a keyword (assuming all the original metadata is present and correct of course). As a bonus tip, search for #desktop to see all of the pictures uploaded from your computer rather than a smartphone.