So if your account existed when the Mann vs Machine update came you get a genuine Steaming Pack! (Randomly painted all the same colour/color) You can re-paint it if you want.

If you're wearing the WHOLE Steaming Pack you can do the steaming pack taunt, it turns you into a robot and does a random regular taunt that you would do if you were holding the regular weapons.

You can put a decal on the Pick.exe top rectangle.

You can't get the steaming pack as a drop!

You can craft these weapons by having a strange stock soldier weapon with a refined to get the equivalent Steaming Pack weapon. This crafted weapon can be painted but only with certain colours/colors.