Originally made of coral red and black hard rubber, the Duplex range was expanded in around 1929 with the introduction of celluloid. The new pens, advertised with the slogan “Aurora Duplex –Infrangibili – in Aurolite” (Aurora Duplex– made of unbreakable aurolite), came in five versions and five colors: marbled red,marbled green, marbled blue, and marbled black celluloid and red coral hard rubber. A shade of black and pearl arrived on the scene sometime later.
Aurora varied the Duplex by changing the style of the clip and cap bands. One version of the Duplex has a single gold-filled band with a laurel leaf–style clip. The variant has a more modern clip, attached to the pen under the hard rubber finish of the cap, but retains the single cap band. A version with three small cap bands sports a clip with rich floral decorations, further enhanced by a pierced band below it. The variant with three cap bands can also be found with a plain clip with a band.