From TF2 Wiki
The Wiki Cap is a headwear item wearable by all classes. It was released in the September 30th (2010) Mann Co. update. It appears as a team-colored cap bearing the Team Fortress emblem, and is similar in style to the Soldier's Stout Shako, albeit it's size is somewhat less exaggerated. It is listed as "not tradeable".
- This hat is a type of peaked cap.
- This hat resembles M. Bison's/Vega's Dictator cap from the Street Fighter franchise.
- This hat is similar to the Soldier's Stout Shako, the difference being that the Stout Shako is taller and has a flat top.
- This hat is not giftable.
- The hat has a sparkling effect mostly seen on Valve self-made or Community contribution items.
- As of 11/26/2012 only 128 of these hats exist one of which is self-made.
- Despite many players' wishes, Valve has stated that they will not make the hat tradable.
- This hat resembles the Soviet Russian police cap.
- This hat shares its design with that of The Milkman.
- This hat is now paintable.
- This hat has a slight resemblance to the Team Captain hat.
- This hat can be worn by all Nine classes.
- This hat is team colored.
- This hat is worn on the head.
- This hat shares its design with that of the Grenadier's Softcap.
- This hat shares its design with that of the The Superfan.
- This hat shares its design with that of Bill's Hat.
- This hat was entirely based off of the Direct Hit.
- This hat is a miscellaneous item.
The very first owner of the Wiki Cap was a user named Pilk.
About Pilk: He is a bureaucrat of the Official Team Fortress Wiki. He was given access to an API call to drop hats to a given Steam ID. Robin asked him to test it on himself first.
After this, wiki caps have been awarded to members of the Team Fortress 2 Wiki who display quality and commitment to it. There is a forum group labled OTFWCHL which all Wiki Cap owners are invited to.