Amilcare Guarneri, Milan

This was an old-established firm producing postcards before 1900. Amilcare also acted as the Rotophot agent in Italy. Amilcare was succeeded by Arturo in running the company. The entry in Annuario_industriale_della_Provincia_di Milano 1933 (see Google Books), about the time of the third example card, reads:

GUARNERI AMILCARE - Milano, via M.Melloni, 17. ...
Proprietaro: Arturo Guarneri - Edizioni cartoline.

Undivided Guarneri cards often also have the round "Stab.Galileo Milano" logo (qv), this will have been the printer.

It seems Guaneri was also the publisher of cards with marks GAM, as discussed there, and also Clou; and maybe other marks as well.

Guarneri Guarneri 0547
Guarneri Rotophot agency
Guarneri 2427 posted 1934
Colombo kids series