Well you know the shading is different on stuff like Guardians and Cents and SM. The faces of Arrcos and Studs are slightly further from the edge and the pips are wider than Bikes... Jumbo Index cards will have different designs too, as will various decks designed for people with some degree of seeing difficulty.
I couldn't find any with a quick search of Vodkas - but basically their pips are grouped together, think the Pip Trip gaff card where all four pips are in a corner.