The Bon Trading Co. reproduction has "Made in Italy" engraved underneath (see here).
(Giordano Robbiati never stamped neither "A" nor "B" models, see here)
The Bellman CX-66 reproduction has the name "La Sorrentina" on a black badge (see here).
(Alfredo Robbiati's "La Sorrentina" were golden badged, see here)
The Indian reproduction has a boiler Plug that comes out a centimeter away.
(Note: On some of Giordano Robbiati's Model "A", the security valve is placed there, see here)