Jack Campin said "Most surviving and reproduction cornetts are made of wood (either one-piece or glued-together strips)."

Whilst it's true that most high quality reproduction cornetts are made of wood, by far the most common ones you see are made of resin and are considerably cheaper than the wooden ones.

I can hear a slight difference in sound quality between the two, but that may be more because those players who go to the expense of buying wooden instruments tend to be the better players who take cornett playing a little more seriously. (A generalisation which is as accurate and inaccurate as any generalisation can be).

Cheers,

Weasel