The Valve quality is assigned to certain items that are given to Valve employees. In some cases, they possess the Flying Bits particle effect. Because of their nature as items of developers who have unlimited freedom, they may possess stacked attributes as seen in the backpack example; however, these additional attributes are not part of the Valve quality itself per se. In fact, some Valve quality items may be completely identical to a Normal or Unique quality weapon aside from the name. The plethora of buffs on some Valve weapons are, on rare occasions, "used to their potential" on public servers, when one can expect the entire enemy team to obliterated by the mischievous employee. However, the unfortunate victims of the community tend to receive their deaths very well and with a sense of awe due to the hilarity of the situation.
The Valve item shown in the backpack example is Robin Walker's Rocket Launcher.
The hexadecimal color code for Valve items is.
Robin Walker rampaging with his Rocket Launcher in a public server:
Another video of Robin Walker with his Eyelander
Flying bits attached to the Escape Plan.