Immediately after WWII Omas reviewed its lines of pens and replaced the old Lucens/Extra Lucens plunger filling mechanism with the more modern and easier to use piston.

The new piston was used for a line of pens which retained the old design with the roller clip and the slightly tapered ends. They were marked simply "Omas Extra" on the barrel and were marketed in three sizes: 555 ( lady), 556 ( standard/senior ), 557 ( oversize). Colors for this model were jet black, gray pearl, arco bronze and arco gray.

This model was the link between the old traditional products and the more modern pens which would be introduced in 1948. It is a sturdy and reliable piston filler with an elegant design.

This Omas Extra 556 Piston filler in black celluloid is a perfect daily writer with a very responsive and flexible nib.