ok let me let you into a secret ....
having worked in the 'colectables' industry you learn a bit
pokemon "rare" cards
each pack contains the same number of cards
all are the same size and weigh the same appart from the metal coated or shiny ones
so weigh each pack remove the shiny ones and hey presto a full set of rare cards
other chase cards have differing methods the normal one is ....
imagine a card factory one huge printing press printing thousands of the buggers now they are printed and sorted the 'normal' packs make their way into a rapping machine which puts the foil packing on (the bit you rip open and throw away )
now the 'chase cards' the ones you want are on a different conveyor belt on a different machine so the foil is slightly differently sealed
they are then sorted into boxes usually of 46 with one chase pack in
so if the petrol station attendent has half a brain ......
he looks at the back of the un opened packs finds all the different packs
opens it and sells the contents on e bay
s'easy
anyone want to swap the audi tt wheels for the car