Its a large tent (sort of party tent), Swiss dealers only, of course the guys from Lengenbach and Binntal in general, pretty local. It is not very big, about 30 dealers? Might not be worth travelling there from Zürich, but nice anyway and you might combine it with a Binntal collecting trip.
Well, just follow the link, you get all infos, including pics from the last ones.
Cheers,
Stefan