This is a Mabie Todd Swan Visofil VT 340 / 76 Green & Silver Pen c. 1937-1942. Mabie Todd introduced its ink visible barrel pen, the Visofil VT, in September 1937. The VT, while appearing similar to a Parker Vacumatic, operates without a blind cap, as the plunger retracts by unscrewing from the base of the barrel. Internally, the diaphragm system is designed differently than the Vacumatic, to accommodate the retractable plunger. Visofil VT pens were made with a celluloid cap and barrel in four colors: Black & Clear, Green & Silver, Ruby & Silver, and Black & Silver (or Grey). The cap and barrel end are matching opaque celluloid and the barrel center is transparent patterned celluloid. The cap top and barrel end cap have a slight pointed crown. The 5 1/16 inch long pen has gold filled trim, including several rings on the cap and barrel. The 14 karat gold Number 3 nib was available in all the Mabie Todd sizes and styles. Visofil VT pens are uncommon, likely due to the difficulty of repair.