What's The Safest Way To Crack Proofs Out?

I have had good luck (seriously) with a hammer and medium sized wood chisel. I place the
plastic holder with the narrow end up, exposing the seam. I place the chisel at the corner of the
plastic holder on the seam and tap gently, gradually increasing the strength of the tap
till the holder begins to separate. I then gently pry the two sides apart. I have a soft surface
ready, wear gloves, and transfer the coins to a safe holder.

So far, so good. I have enjoyed the tips, real and tongue in cheek!

The coins in the picture are the bicentennial silver proofs that come in special individual sonic-sealed airtites that are very difficult to open. Screwdriver will probably not work. Knife will probably not work. The easiest method on these are to take a razor knife and carefully score around the line where the two halves of the capsul come together. Then find a bench vise. Wrap the capsul in a thin towel just for safety and place in the vise. Close slowly until you hear a slight snap of the plastic cracking - don't apply too much pressure - you just want the seal to crack. Rotate coin 90 degrees and close vise again until you hear a soft crack. Rotate 45 degrees and again, then 90 degrees and again. Take the capsul and look and see if there's any separation. If so, use a screwdriver and gently pry the capsul open.

I ruined a set of these before I read this method somewhere else.
Since then I've managed to not ruin any.

Remember: these are not normal airtites or modern mint capsules. They are sonically sealed very tight. The normal methods of opening airtites won't work unless you get very very lucky and have a capsule that wasn't sealed properly, which out of the 6 sets I've opened, I've never found.

Thanks for the clarification. I had thought they were the normal mint proof set plastic
enclosure. I will be on the lookout for this type of enclosure. I have not seen one.
How is it different from the one pictured below? Where does it "come from?"