First let me say that the military doesn't just use American, and frankly of the padlocks I have seen the American tends to be the better brand (coughs the word brinks). For those who haven't been in the military, the world of the lock is more of a "Hey don't touch this" in the military then usually a security feature. While yes this helps prevent theft and it does happen most padlocks are meant just to keep people out of supplies, personal belongings etc. However most times you could leave the lock off with a do not disturb sign and be just as effective, it all depends on the unit, people etc. One of the big things the military like is a the idea of security, and most contracted locks (not purchased by the unit for the unit) is the ability to change out the core of a lock to a new key at a moment notice. You will see this in more secure locks, but American is one of the more common ones, and easiest to dismantle as you will see.
This poor lonely lock was taken off a shipping container by its owner, the key was taken with them, and the lock tossed into the dirt. It stayed out in the elements for probably 2 weeks before I found it, and decided to give it a good cleaning.
This next photo is the base of the lock note the small round bump.
It is hard to see but inside the lock is a Philips head screw, all you have to do is unscrew this to take the lock apart, but when locked you wont be able to obviously.
Base plate and screw
Here is the core still in place in the lock, note how the screw prevents the core from shifting.
The core itself from a rear perspective, this should give you a idea of its function with the next photo.
Lastly inside the lock, and on the left side you can see the half moon area which lines up with the rear of the core and allows the padlock to function
Hope some of you enjoyed this, I took these photos for someone else, but figured I would post here as well..