This is a Conklin "Three-Fifty" brown and black marble pen, c1934-1935. It is shorter and narrower than the higher priced Endura line and has a simple Conklin imprint stamped on the barrel. These pens are shorter, at about 5 inches long, and have an earlier clip than the new 1935 patent clip, which helps dating. The nib is the earlier Conklin Toledo nib. Three fifty was the selling price, $3.50 and matching pencils were $2.50.