I've cracked open quite a few. An easy and safe technique a friend showed me is put the edge of the slab in the crack between the door and frame of a safe and slowly close the door. Takes two seconds and it pops the seal around the edges. Nice and clean. Guy
I confess to having done this a hundred times. Here are tips: PCGS - Very rigid, hard plastic. Simple, 3-second solution...use bolt cutters (see images below) Others - Wrap the slab in a towel, place it against a hard surface, and use medium-force taps around all sides. Maybe 10-20 blows. If you do this well the slab will look reusable! (see image below) But of course, I'd never do that. Lance.
I've cracked 10 out of PCGS and NGC slabs for my Morgan set. I was only nervous with the 1885CC. A hammer works great.