This is a Conklin All American Black Self Filling Rubber Sack Pen c1936. This 5 inch long model also came in Green Etched and Red Etched celluloid and sold for $1.95 with a $1.00 matching twist action pencil. Both the clip and lever are stamped with their patent numbers. The standard gold nib is plain and stamped simply ALL AMERICAN, with no hallmark. The barrel imprint, not shown, reads ALL-AMERICAN over A PRODUCT OF CONKLIN over TOLEDO, OH U.S.A. These streamline All American pens have two imprints, slightly different.