There's one way to find out... My owners handbook calls it plastic. If you can buff out a scratch it's probably Acrylic, Polycarbonate the scratch is usually permanent.. I have the stock Triumph Summer Screen and have been able to buff out scratches on it. Good Question??
A bit shocked if they used acrylic on the stock screens, a bit of a liability issue, there is actually kind of a good reason that PC is the predominant material in use for windows on vehicles.
Kidding. I don't know what the stock screens are made of. My stock screen is stored away and I have a Clearview. They seem the same. The Cee Bailey I had on a TBird was acrylic seemed different than the stock screens and Clearviews I've had on Triumphs since 2004. Why would Triumph use National? US company?