Sticks and snails and .... No, no. It's reasonably certain that PCGS and NGC slabs are acrylic (polymethacrylate). PCGS stated a while back that their slabs are made of acrylic (see link). It's possible that they've changed, but I doubt it. The only other reasonable possibilities are polycarbonate and polyester. Both are much tougher than acrylic. Watching a coin being broken out of a slab is proof that the slab is not polycarbonate or polyester. It would be fun to watch someone try to break a polycarbonate or polyester slab with a pair of pliers, nippers or hammer. A saw would work quite well though. Some other clear, rigid plastics are even less likely. Polystyrene is too weak. Polyether ether ketone (PEEK) is really strong but very expensive. Clear, rigid PVC is not all that clear and not as rigid as other plastics above. However, there are different varieties of acrylics as well as surface coatings than can affect things like scratch-resistance and chemical sensitivity. These particulars are trade secrets of the grading companies and their plastic suppliers. Acrylics have been around for more than 70 years. Lucite and Perspex are common brands. Samples that have been reasonably well protected have shown little change over many decades. The above refers only to the outer casing of the slab. The innards are probably polyethylene and/or silicone polymers. These are lightweight, soft, inert plastics suitable for space-filling and holding a coin by the edges. Cal --------------- link: https://www.pcgs.com/news/Its-More-Than-Just-A-Piece-Of-Plastic Nice link comparing acrylic and polycarbonate: https://www.theplasticpeople.co.uk/blog/the-differences-between-acrylic-and-polycarbonate/
