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My guess is this: There is a kids game in sweden where someone hides something while the other kids sit in a room close by. Then when they come back he says where its located, fisk, fågel eller mittimellan (fish, bird or in between).
In my twisted mind that sign kind of looks like a quake-symbol... Even though I must say that it is probably the crappiest attempt at a quake-symbol I have ever seen.