Classic;
(1) Of the highest Class, Most representative of the excellence of its Kind.
(2) NA here, applies to the Arts.
(3) (Colloq) Famous as traditional or typical.

By definition 1 then only the highest graded guns by American makers could be called a Classic American Gun. By definition 3 a Trojan, Sterly, Field, etc or even a Crescent could be a Classic American Gun. A Purdey or a Darne would not make it on either account, simply because they are not American.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra