I have spent some time wrestling with that question (it's not easy to identify these little Mexican plants) and would say the generic Graptopetalum listing is probably where all but the first two pictures should be placed, until someone can pin down a more specific ID. If you have seen the flowers and they are open like the ones on this page
then you can be certain the plant is not a Graptoveria (the Echeveria parent has closed, bell-like flowers and this feature transmits to intergeneric hybrid offspring).
