Problems with Frege's Argument

Recently, I was thinking about what could the actual force behind Frege's argument for numbers as properties of concepts be. Let us suppose that the argument passes by and we agree that numbers are in fact properties of concepts. Does this necessarily lead us to conclude that numbers are not and could not be properties of physical objects as well? I am not sure. Even if numerosity turns out to hold as property of [a] concept[s] this does not exclude automatically numerosity as property of the reference of an concept. I think it is important to distinguish between numerosity and attribution of numerosity. Although attribution of numerosity might turn out to depend almost entirely on concept or conceptualization this still does not mean necessarily that numerosity is not a property of physical objects. It might turn out to be the wrong value of the numerosity [due to wrong attribution or coordination, in the Reichenbachian sense, for example] but still it could turn out to be numerosity of some kind, not necessarily the traditional one. Task to work on: formulate reductio of Frege's argument.