Referencing a board game rule book
The point of referencing is to allow others to determine what you've referenced and to look it up in turn. 

Harvard has tools for citing multi-media formats, such as board games. 

Inline: ([Rulebook] 1986). 

Biblio: [Rulebook] 1986 Labyrinth (boardgame), Ravensburger. 

Consult a full style guide and model off the nearest multi media work, for example, album liners to a CD.

Are you sure 2007 is really the date of the edition and not the printing?

(Kobbert 2007).

Kobbert, MJ 2007 '[Rulebook]' Labyrinth (boardgame), Ravensburger Spieleverlag.