In 2007, Series 4 debuted with just fifteen models. However, in recognition of the 40th anniversary there were two packaging versions available - models came with a collectible metal badge (featuring a portrait of the involved vehicle) or were sold alone as in the previous three series. Models included a "VW Karmann Ghia", a '"68 Mercury Cougar", and the ""Red Baron" hot rod". For its 40th anniversary in 2008, Hot Wheels celebrated the making of its four billionth car with the production of a diamond-studded model worth US$140,000. It had 2,700 diamond chips, a total of almost 23 karats, and was cast in white gold, with rubies serving as taillights.