Satin lustre in words....
well, with most pearls you want a mirror finish, like the finest polished metal or..a mirror. so you can see your reflection. It will be sharp and hard as a surface. With SS satin lustre, you can have lots and lots of shine still but it is the shine of great satin silk fabric.
Sort of like a camera lens with a smear of vaseline...same image but not focussed the same way...errrr. In any case, low lustre is low lustre, and there is no mistaking the difference between low and top grades
once you have seen the different pearls you'll understand maybe more clearly...