We aren't certain about the official Esterbrook letter designation for this model, but it relates to the Esterbrook J-series of fountain pens. Our vintage pencil is a lovely mint green and still in good working order. Cap actuated, you click the tail cap to advance or retract the .9mm lead. A couple spare leads are under the tail cap, but the eraser is long gone. A crisp imprint greets you on the barrel, and it only has light wear from use. 12.3cm.