The basic riders that are the most common and usually made of lamb except for the one just posted. In other words you'll see a lot more jackets in lamb than calf but if you were to look at every model presented in the collection, most of them are in calf. That's my experience but I'm not a SLP nerd, just went to the places where they sell those in Paris (Printemps, SLP stores) and in various SE asian cities (I like to look at luxury brand stores in asia, it's just so weird how they perceive the stuff).
Well they don't have the primary references so for them everything is superflat, it's all on the same level and only refers to fashion or the superstars who wore the actual articles. In other words a SLP perfecto isn't 80s rock'n'roll and american but something Kanye or some asian popstar wore. Poell is like Chanel is like SLP etc.