A 'California' AND a GS . (some history on the California and Colorado Buicks found here: http://webspace.webring.com/people/eu/um_4456/california.html Wagon is for sale in Germany at almost 15,000 euros
Cool car but I thinks it's a Skylark, it's not a Sportwagon for sure. Buick Sportwagons have the roof windows like the Vista Cruisers. The roof rack is hideous, looks like it's from a boat. Buick GS California wagon? Probably made about as many of those as they did 442 wagons, it's a one of none.
That's because the model isn't listed when you want to sell (or search for) a Buick Special, so for some reason the seller decided to list it as a Riviera...
There is a remote chance (?) it could have been a dealer instaled promo option. It has happend to several cars of that era and there is no trace of them in any factory recoreds. The Mustang Stallion is one example.... http://allstangs.com/blog/1967-stallion-edition