If you have a large, furry cat and you aren’t sure whether they are a Maine Coon or a Norwegian Forest Cat, look at the shape of their eyes. The former have lynx-like eyes, while the latter have almond-shaped eyes.
Also, look at the tail. The American breed’s tail is fluffy and tends to point up into the air. The hair on a Norwegian Forest Cat’s tail is even longer, and it tends to snake along behind them.