In 1910 a draughtsman named Romano Cattaneo was given the job of coming up with a badge for a new Milan-based company, ALFA. The story goes that as he was waiting for a train at the Piazza Castello terminus in Milan, he gained inspiration from the red cross and off the coat of arms and flag of Milan and the Visconti family’s biscione (human child-bearing serpent) coat of arms emblazoned over the great door of Castello Sforzesco:

Visconti family’s biscione coat of arms
In 1918 after the company was purchased by Nicola Romeo, the badge was redesigned with the help of Giuseppe Merosi, including now the City of Milan’s emblem and that of the Visconti family in a circular motif, bordered by a dark blue metallic ring containing the inscription “ALFA — ROMEO” and “MILANO” separated by two Savoy dynasty knots to honour the Kingdom of Italy.

Milan Coat of Arms
After the victory of the P2 in the inaugural Automobile World Championship in 1925, Alfa added a laurel wreath around the logo.
In 1946 after the victory of the Italian Republic Savoy knots were replaced with two curvy lines. The name “MILANO”, the hyphen and the Savoy knots (lines) were eliminated when Alfa Romeo opened the factory at Pomigliano d’Arco, Naples in early 1970s.
Photographic images of each major badge evolution, with a brief description follow below:

Size: 65mm in diameter. Note the absence of the word ROMEO, and the acronym style representation of the word A.L.F.A.

Size: 65mm in diameter. Nicola Romeo has now acquired the ALFA company and reorganised it after the First World War, adding his own surname to the badge, whilst removing the acronym style of the word A.L.F.A

Size: 75mm in diameter. To commemorate the Alfa Romeo P2 winning the first World Motor Racing Championship, the Alfa Romeo badge was surrounded by a laurel wreath in respousse metalwork. In 1930 the diameter of the circle was reduced to 60 mm and this remained unchanged until 1945.

Size: 54mm in diameter. When the Italian monarchy was abolished, and the country became a Republic, the Savoy dynasty bows were exchanged for two wavy lines, and the badge’s diameter reduced to 54 mm. In 1950 a new badge in enamelled brass but with the same diameter was introduced – please see top of page. In 1960, the same badge design, directly above, began manufacture in plastic.

Size: 75mm in diameter. Since the build of the Alfasud factory in Pomigliano, near Naples, the word MILANO has not appeared on any Alfa Romeo badge – although it still retains its two famous Milanese symbols, surmounted by the words ALFA ROMEO.
Source’s - http://www.wheelsofitaly.com & http://www.alfalegend.com