I'm not so sure the newer ones are much better to be honest. I tried one recently and the cast was horrible.
OhWas it made of resin or glass? If it's still resin, IR pollution is likely to be around.
Lee told me how hard they tried to make a ten stopper out of resin, and failed. If they can't do it, nobody can. Lee's glass Big Stopper is made for them by a specialist manufacturer.