It's pretty easy to tell when the microwave fires up, and that was one with a good seal on the door. Imagine what an old one would look like.
Anyway, as long as you stay a few feet away from the antenna you'll be alright. Just make sure you stay under the fcc limits. If you're a guy, I'm guessing you are, we don't get too many chicks here, keep it away from your eyes and balls, they are the most sensitive to microwaves.