I've seen countless married couples at restaurants and you have no idea how many times I've envisioned, no, fantasized about a conversation like this - me going up to their table and, well, opening a dialogue:
Excuse me, sir, I'm sorry to bother you - hope your meal was great, those ribs look like they were dynamite. (looking shyly at dude's female companion, almost whispering), hi sorry to intrude.
But sir, I've got to ask, you're totally married to her, right?
Yes, yes I am. That's my wife. Why do you ask?
I could just tell by that disinterested look on your face the entire time that she was talking to you, that you are married to her. That she's your wife. Enjoy the rest of your meal, cheers.