2013 Fort Mchenry Quarter Error?

Your coin is showing Machine Doubling on the incuse devices. When we see machine damage/so called doubling, on the raised devices, it reduces their size. But on the incuse devices on the ATB Quarters on the outside edge are incuse, they enlarge the devices. So what you have is an example of Machine Doubling on incuse devices. The devices are raised on the die making them incuse on the coin.
An few examples of Machine Doubling on incuse design:



So die movement enlarges these devices.

On a true doubled die, these would reduce in size as illustrated by a 2013 DDR cent.
Note the raised devices:




Note the incuse devices:

Check out coop's post above, it should help to understand what you have. It's not considered a collectible error.

A lot of what was seen on the above images is called metal striation lines. What does that mean? The striation lines happen because of the die movement during Machine Doubling moving. That is probably the biggest collection of metal striation lines I've seen posted. If you have a stick of warm butter, take a paring knife and hold the knife with the sharp edge held downwards. Then slide the knife parallel across the butter. This edge of the knife will leave the same lines across the top of the butter. If can be use in forensics to show the pattern of the knifes edge. This Machine Doubling rubs the edge during the strike leaving these lines on the incuse devices as seen above.



So when you see these lines, it is Machine Doubling that caused these.

I feel taking information a little at a time, and then add just a bit more, is the best way to learn. If you get too much, then it hard to grasp. Just a little bit more, adds just the right amount.