The last series produced in celluloid, the [[Columbus 90]] was introduced approximately in 1951, and made both as [[piston filler]] or with a special [[button filler]] with the bottom back not removable, similar to the ''[[push-knob]]'' of [[Montblanc]]. The production of the '50s saw the abandonment of celluloid for the use of cheaper molded plastic, and the production of [[Columbus Anni '50|models]] with [[hooded nib]] and cheap plastic pens for the student market. | The last series produced in celluloid, the [[Columbus 90]] was introduced approximately in 1951, and made both as [[piston filler]] or with a special [[button filler]] with the bottom back not removable, similar to the ''[[push-knob]]'' of [[Montblanc]]. The production of the '50s saw the abandonment of celluloid for the use of cheaper molded plastic, and the production of [[Columbus Anni '50|models]] with [[hooded nib]] and cheap plastic pens for the student market. |