Size: Capped - 5 1/8 inches; posted - 6 inches.
The CX100 pens were manufactured in the late 1950s and early 1960s; a cartridge pen designed to compete with Sheaffer's School Pens, they are now fairly scarce, especially in the UK. Unlike many Esterbrook models, I don't think any of these were actually made in the UK; this one has the "Made in USA" imprint. This pen is in excellent condition, and cannot have been used much. It has a chrome plated cap with "ESTERBROOK" imprinted down the stem of the pocket clip. The barrel and section are made from glossy black plastic, and the nib is a Nol 2556 renew-point. These nibs just screw in and out and are interchangeable with the other renew-point nibs from earlier Esterbrook pens, and also with some Venus nib, and some of the earlier Osmiroid and Burnham nibs. This pen is a cartridge-fill pen. Although the Esterbrook cartridges have not been available for many years, the standard International ink cartridges can be persuaded to fit, though it is a bit tight. A better and easier fit can be obtained by using the mini Parker ink cartridges, or the Moonman ink cartridges (link below) which are designed to use a wider diameter nipple.
I have fully serviced this pen. The nib is very smooth and writes with a very nice wet and very fine line.
An unusual Esterbrook model - on the rare occasion I come across one of these it is nearly always used to death. This one is a happy exception.