Short phrase for something that is recognised but not identified?

I've had a long discussion with people on the differences between recognizing a face in a crowd (I know I've seen that person before) and identifying the person you see (That's the waitress from the diner).

Is there a short phrase for those faces (or other objects) that you recognize but do not identify? For example, when watching a TV show I frequently know I've seen an actor/actress before but not where and certainly with no knowledge of their name.

Unidentified covers those I do not recognize as well as those I do. Familiar faces works the other way in that it would also cover those I can name, but it is much closer to the sort of phrase I am looking for.

How about familiar, "possibly known but imperfectly remembered"? As in, "that actor looks familiar!"

Edit: this has a different meaning than the phrase "familiar faces." For example, if someone walked up to me in a crowd and said, "You're a familiar face!" I would expect that person to know me well, at least relative to other people in the crowd. On the other hand, if the same person said, "You look familiar," I would probably try to help him figure out whether he actually knows me or not.

How about the phrase ring a bell?

ring a bell: to seem at least vaguely familiar: His face rings a bell

ring a bell: to cause for someone to remember something or for it to seem familiar; to seem familiar: I never met John Franklin, but his name rings a bell; Whenever I see a bee, it rings a bell. I remember when I was stung by one