A favorite among vintage collectors on a budget. Esterbrook had been around a long time (since before the Civil War), producing steel dip pen nibs. It enjoyed a period of success making low end fountain pens (the J series) but they could not compete with ballpoints and exited the market in the 60s. As far as I know, Esterbrook no longer exists in any meaningful form today.
The most notable feature of Esterbrook pens are the interchangable nibs. The nibs screw out of the section and can be swapped out easily. Esterbrook made over 30 different nibs covering a wide variety of uses, from accounting to penmanship to general writing. This allows you to have a single pen with several different writing styles by simply swapping out nibs as needed.
Esterbrook Pen Gallery
Esterbrook J series
Most Esterbrooks you find today will be one of these. They came in a couple variants, from the full-size J to the skinnier LJ or the shorter SJ. All are lever-filled and use the same lever mechanism. Studious collectors will note minor variations in the cap jewel; this can be used for dating and identification purposes.
Here are some examples from my personal collection.
Esterbrook J transitional 1944-1948
Esterbrook Cartridge Pens
Esterbrook also made cartridge pens just before they folded. They are not as common on the vintage market than the J series and they use a cartridge format that is no longer being manufactured. They use the same nibs as all Esterbrook pens, though.
If anyone has supporting documentation for these pens, let me know. My best guess is that they were produced in the 1960s.
Esterbrook cartridge pen circa 1960s?