The "slab" was adopted by the coin collectors and the sports card collectors as a way to "certify" the grade of items. The "slab" can be opened but when the seal is broken the grade is no longer certified. The intent was to rely on "experts" to provide a 3rd party grading service - for a fee of course. It has created a situation where very tiny differences in condition can lead to huge differences in price - which of course leads to "grade shopping". If you don't get a high enough grade you just open the slab and submit it to another service and hope for a better grade. The whole process changed the hobbies - it took a lot of the fun out of it. It was a great service to our hobby that they resisted the attempt to get slabbing adopted. My thanks to all those involved.