Each branch of the military has different buttons and symbols to identify themselves: the Army, Navy, Coast Guard, Marines and Air Force. Different officers from different branches of the military wear different military buttons. If you are needing to determine which military buttons bear which significances, you can do so by keeping a few rules in mind.
Look for an eagle on the button. It's usually gold, but some of the buttons can be brass. An eagle, especially in gold, signifies the button used for the Navy. The eagle is usually full and has its wings spread out. Some of these buttons have stars around the eagle, but the eagle is the one telltale sign of a Navy button.
Identify the Coast Guard military button by looking for an anchor. It is usually surrounded by a cloth or chain that is the same material as the anchor. They come in varying colours, but the most popular type of button is a silver anchor with a gold chain or ribbon.
Use the eagle to identify the Air Force military branch button. This time, though, the eagle will be perched on top of a symbol of another eagle and will have stars surrounding it. It's smaller than the Navy button and is usually brass, hanging on the top of the left or right shoulder.
Check for an eagle a third time to identify the Army button. It's much the same as a Navy button, but the eagle on an Army military button is normally smaller and has a symbol above its head. Most times there are no stars surrounding the eagle on the button, but it is bright gold like most Navy buttons are.
Find another eagle embroidered in gold for the Marine Corps button. The eagle is facing a different way and you can see the wings clearly, and the eagle has a chain surrounding it with an anchor hanging off the chain. There are subtle differences between military buttons, but this one is easily recognisable. The top half of the eagle is surrounded by stars.