This is a Parker Trench Pen in red brown and black mottled ebonite c1916-1918. Parker's Trench Pen is an ink dropper pen with a long end cap intended to hold ink tablets. The barrel is essentially the same as a self-filler without the button fill mechanism or the hole in the bottom of the barrel for the button, as can be seen in the photo. To refill, the user would take one or two tablets out of the end cap, unscrew the nib section, drop them in the barrel, add water, and the tablets would dissolve, making ink. This eliminated soldiers having to carry ink bottles. Parkers 1916 patented clip allowed the pen to clip to a soldier's pocket and be able to button the pocket flap. The 4 9/16 inch long pen has a 5/8 inch long end cap. The Number 2 solid gold nib is unhallmarked. The clip is chrome plated. These pens were also made in black and red hard rubber. Parker's 1918 advertisements states these pens sold for $2.75 and up, the clip was an additional 25 cents, and a packet of 36 ink tablets was 10 cents.