Colonel Autumn's uniform

Col. Autumn's Uniform is the service uniform of Augustus Autumn. It consists of a jet black uniform and a resistant, tan trenchcoat. It is based on pre-war officer uniform designs.

Obtaining
Method 1) There actually is a way of getting this outfit before the end of the game. During the Waters of Life quest after Colonel Autumn supposedly "dies", you can grab his belongings as long as he falls near the door. You must face directly towards the body with the cursor directly on the body in first person view. Once this is done, hold down the button that changes the perspective and you should be able to rotate the camera. Rotate the camera half-way and you should see a "Search Colonel Autumn" message. Voila! You can also search Dad and possibly everyone in the room if they fall close enough to the wall.
 * Colonel Autumn does not have his laser pistol during this part of the game. [edit: (360)other platforms unconfirmed. You can obtain Col. Autumn's unique pistol at this point, although when you see him later on he will have recovered both his unique armor and pistol.]

http://www.youtube.com/watch?v=wKyTlV75xY4

(Method 2) If you have missed your chance in the above method you still have another. After you have finished the American Dream Quest (the one at Raven Rock) and BEFORE you activate the robot Liberty Prime (aka the very last mission) fast travel to Rivet City. Once here travel West to the Jefferson Memorial and you should see the blue energy shields. Since you should be coming from the West side go up to where the energy shield cuts off and where the generator is, make a save here. The reason for the save is that when you are jumping over these rocks it is possible to get permanently stuck, any who continue jumping and you should make it over the rocks. The hole in the rocks is under the "stairs", not between the stairs and energy shield generator. Once that is over make your way inside the Gift Shop and into the Rotunda (there will be Enclave Soldiers in the gift shop). Col. Autumn will be standing in there like he is on the final mission but he will not talk with you. You now need to reverse pickpocket a suit of armor onto him that is in good condition. After that leave the room and then re enter, Col. Autumn should be wearing the suit of armor you just put onto him allowing you to pickpocket his outfit.

Method 3) [For Xbox 360] after the lethal gas inside the chamber kills Col. Autumn, your father, and the guards inside, grab the barrels that are around the opposite side of the rotunda. Set them up just outside the locked door where the Colonel and James die, so that you are able to climb them to get on top of the rotunda. You must now sacrifice one of your mini-nukes (hopefully you have a Fatman) to fire towards the statue in the middle. The walls around the statue are non-clip, so the mini-nuke will fly through harmlessly. With proper aim and maybe a few reloads (heavily suggested you save once on top of the rotunda), you can blast the bodies inside closer to the door, after which you can use a technique similar to that outlined in Method 1. If the bodies are close enough, you can merely face the door at an angle with bodies against it and it should allow you to search them. If they are further away, you may have to crouch, enter third person, and face various angles (most of which do not face the door).

Note: DO NOT walk through the nonclippable wall! You will fall into the area, with water at the bottom, with no way to escape. A Reload is the only cure

Note: The area just above the computer your Dad uses that explodes is what gives off the radiation. If standing in the proper place, you can accumulate 50+ rads/sec.

Sub-note: It IS possible to search the scientist and guards as well, but you should be content enough with searching Dad and Col. Autumn, since the others inside carry common armour/weapons.

Method 4) This is done during the Waters of Life quest after the Lone Wanderer's Father has caused an overload of the Jefferson Memorials systems and everyone inside has collapsed. Now you walk up to the airlock door and switch to the third person view which shifts the camera slightly over the right.  Hold down the button that changes view and push the left analog stick forward slightly so that the camera is hovering just behind your right shoulder.  This makes the process a lot easier.

Now get right up against the airlock door with it on your right side and crouch down. Right away you should realize the "search dad's corpse" option, you can take Dad's Wasteland Outfit as a memento of your time together if you haven't gotten it already by some other means. But of course the real prize is Colonel Autumn's gear but Dad's body is in the way. So while continuing to hug the airlock door "grab" his body and move forward, pulling it off to the side. Now move back to where Colonel Autumns body is and you should be able to just about reach his motionless corpse.

Method 5) Another way to obtain this uniform is to glitch into the Jefferson Memorial before the final quest (Save before getting past the barriers.), then sneak past the Enclave troops in the memorial, then kill Autumn in the rotunda, make it where his weapon doesn't fall into the water, the loot his body. When you do decide to finish the game, kill the Enclave troops that would normally guard Autumn to continue. Note: Only confirmed on 360.

Appearance
Fallout 3 only
 * The physical appearance however is pre-war (much like General Chase's uniform though it does have a different color.)