In the early-ish days of the world wide web, one fellow developed a sort of online card game. This particular game had quite the specific audience:
One of the Citroën-internet pioneers, Marcel Reimer, started an internetgame in 1997 by sending some of these cards by e-mail to a number of internet Citroën freaks. They could earn more cards when you answered difficult cryptic questions, the answers could be found on Citroën pages all over the internet. You could also change cards with other participants. The first one to have all 36 published somewhere on the internet received a free meal. That was on a nice and happy night in a restaurant with a number of other participants. (citroen1.info)
The game was titled “Sextet”, with each set being compromised of, you guessed it, six cards, and each of the hey, six again, sets covering a particular model: CX, DS, Méhari, SM, 2CV, and GS! And if you are saying to yourself you only see 5 cards in each set in the above image, you would be correct, so hit the source link and find the missing cards!