In 1946 Omas reviewed the line of his products switching from  the traditional filling mechanism of the Lucens and Extra Lucens models to the more modern and more functional piston. The new piston fillers retained the design of their predecessors, with the roller clip and a the same style of cap and barrel.

The new line of piston fillers was named Extra and was marketed in three sizes: 555, 556 and 557 in a variety of colors among which black, arco gray, arco bronze, blue marbled, green marbled and tortoise brown. The models were fitted with Omas Extra 14 ct nibs.

This Extra 555 in tortoise brown celluloid is new old stock  and has a very pleasant Omas Extra 14 ct nib with a nice patina (it can be polished at wish). The nib is smooth and flexible. I just dipped it to test it for writing as the pen has never been filled with ink. 

The filling mechanism is in perfect working order.