It's a Spanish gun ... El Faisan. I know my uncle has been only shooting 2 3/4" out of the gun for years. When he got the gun, the old timer gave him some shells that were 2 3/4" also BUT I know I should make sure. I was told the 70 on the gun meant it can shoot 2 3/4" . I would like to think that they would be smart enough to stamp what you can shoot.
Paul
Paul