Franklin-Christoph's Model 31 shares features with several other pens–the shape of the Model 19, the recessed nib of the Model 20, and the grip of the Model 40 Panther. This is a large pen that can be posted as it follows the precision posting design of the Model 03, making it a reliable and easy-to-use instrument that offers the best features of its contemporaries.

Model 31s are usually made of acrylic, but today’s pen is a bit special as it's molded from acrylic that’s made to look like glass. The Model 31 Omnis Fountain Pen - Antique Glass has an interesting bluish-green sheen not unlike Coca-Cola bottles of old, and, with years of use, it develops micro fractures that give it a look similar to cracked ice. 

We have a pre-owned Franklin-Christoph Model 31 Omnis Fountain Pen - Antique Glass with an F Leonardo nib up for sale. It measures 13.9 cm capped and 17.2 cm posted. It has general signs of use and some ink staining on the colar, but these don’t affect writing experience. We’re offering only the pen and its converter–no box.