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<noinclude>{{Infobox_Brand|Zerollo}}</noinclude>The ''Zerollo'' was founded in [[1932]] by ''David Dante Zerollo''<ref>it seems however, that he was already active in the fields of mechanics applied to the stationery, holding a patent ({{Cite patent|US|1790037}}) for and automatic letters sealer, assigned into the U.S. in 1931 but applied since January 1929 in Germany.</ref> in Genoa for the production of one of the most original ever made pens, equipped by special telescopic system that allowed alternating between two different pens contained in a single body, extracting either one and then the other.<ref>the idea of a double pen however is not so original, it appeared already in a 1912 patent ({{Cite patent|US|1020221}}).</ref> The pen was protected, according to the manufacturer, by patents obtained from all over the world, but the only known are the U.S. Patent {{Cite patent|US|1893130}} required in 1930 in Italy, in 1931 in the U.S.A. and awarded in 1933, the British patent {{Cite patent|GB|397736}}, approved August 31 , 1933 and the French patent {{Cite patent|FR|728038}}.<ref> in patents are cited as inventors Chelazzi Mirko and Dino Frulli, presumably Zerollo employees.</ref>

<noinclude>{{Infobox_Brand|Zerollo}}</noinclude>The ''Zerollo'' was founded in [[1932]] by ''David Dante Zerollo''<ref>it seems however, that he was already active in the fields of mechanics applied to the stationery, holding a patent ({{Cite patent|US|1790037}}) for and automatic letters sealer, assigned into the U.S. in 1931 but applied since January 1929 in Germany.</ref> in Genoa for the production of one of the most original ever made pens, equipped by special telescopic system that allowed alternating between two different pens contained in a single body, extracting either one and then the other.<ref>the idea of a double pen however is not so original, it appeared already in a 1912 patent ({{Cite patent|US|1020221}}).</ref> The pen was protected, according to the manufacturer, by patents obtained from all over the world, but the only known are the U.S. Patent {{Cite patent|US|1893130}} required in 1930 in Italy, in 1931 in the U.S.A. and awarded in 1933, the British patent {{Cite patent|GB|397736}}, approved August 31 , 1933 and the French patent {{Cite patent|FR|728038}}.<ref> in patents are cited as inventors Chelazzi Mirko and Dino Frulli, presumably Zerollo employees.</ref>

[[File:Zerollo-Small-Lady-LightBlueStriated-Open.jpg|thumb|A ''Zerollo'']]

[[File:Zerollo-Small-Lady-LightBlueStriated-Open.jpg|thumb|A ''Zerollo'' ]]

''Zerollo'' produced substantially only one model, albeit in a considerable number of variants, called [[Duo Color]] precisely by its characteristics of being made by two internal separate pens allowing to write in two different colors. The mechanism, which incorporates the technology used on the classic [[safety]] pens is extremely sophisticated and bears close tolerances, which makes the pen rather weak in terms of mechanical stability. Through an ingenious screw system, the two pens, which are separated by a metal plate attached to the bottom that makes them rotate, are sliding in opposite directions by means of grooves made ​​in the body of the pen, and brought alternately inside and outside the body according to the direction in which you rotate the cap.  

''Zerollo'' produced substantially only one model, albeit in a considerable number of variants, called [[Duo Color]] precisely by its characteristics of being made by two internal separate pens allowing to write in two different colors. The mechanism, which incorporates the technology used on the classic [[safety]] pens is extremely sophisticated and bears close tolerances, which makes the pen rather weak in terms of mechanical stability. Through an ingenious screw system, the two pens, which are separated by a metal plate attached to the bottom that makes them rotate, are sliding in opposite directions by means of grooves made ​​in the body of the pen, and brought alternately inside and outside the body according to the direction in which you rotate the cap.