This is a Parker 51 Special Aerometric pen and pencil set in black c1950-1959. The Special was a lower price point $10 version of the 51 that featured a polished stainless steel cap and a black cap jewel. Parker replaced the 14 karat gold nib with one made of "octanium" to lower the cost. The Aerometric filler is a different design where the squeeze bar wraps around the end of the clear "pli-glass" ink sac. These 5 3/8 inch long pens pens came in black, burgundy, Navy Grey, Teal Blue, and Forest Green.