We use '그거' for the already mentioned object regardless of distance. If there is something near me and far from the person I'm asking and I would ask : "이거 뭐예요?" should she/he say: "그거 ABC" If there is something far from me and near from the person I'm asking and I would ask : "저거 뭐예요?" should she/he say: "그거 ABC"

I guess usually we say 이거 for something nearby and 저거 for something far from us but also when someone asks you 이거 뭐예요? we normally say 그거 or 이거 뭐뭐 예요.