A101 and CA101 Pens
These pens were produced later on in Esterbrook's life and were available in cartridge fill (CA101) or aerometric fill (A101) versions. These date ca. 1955 or later.
The CA101 pens were designed as cartridge fill pens. They either had one long cartridge, or two smaller cartridges which were placed back to back in the barrel. That way, if you ran out of ink, you always had a spare. These came in black, pastel blue, dark blue, pastel green, grey, orange, and a doctor's model in white with a red dot on the end. These were also made as an A101 model with an inexpensive aerometric filler. While not as nice a filling unit as the standard production M2 aerometric, they work well and make filling on the go easy and convenient. Click here for a picture of a box.
Different Aerometric Filling Styles
These are two of the three different kinds of aerometric units found on Esterbrook pens. The top unit is from an M2 aerometric pen and has the Esterbrook name stamped on the metal housing and the words, "Press Bar Three Times To Flush and Fill", similar to Parker 51's. The bottom unit is from an A101 pen and has a much simpler construction with just the word, "Press" on the pressure bar. Late model Phaeton 300's also had an optional aerometric convertor in lieu of cartridges.