Now I've heard of cases where a superceded queen will not be killed off and the new queen will lay along side her mother. But I've never heard of it lasting this long.
Last spring, I bought the marked queen (C shaped marking) from Zia Queenbee. She ended up escaping upon being released in her new hive and I found her being balled at the entrance of another hive. She has always looked greasy, I don't know why. I was not surprised to find that she had been replaced last summer. In her place I found a new queen, the one you see on the left. After seeing her, I didn't keep looking.
Surprise surprise this morning, I was checking this hive for the first time this year and I found the old marked queen. I looked on the other side of the frame and there was the new queen. I did put the new queen on the same side as the old one so I could get a good picture, but other than that, what you see is what you get. No tricks, no Photoshop, no special effects. That is two queens in the same hive for at least six months including over winter.