Waterman 52 BCHR: a quick review for artists

This a review of a Waterman 52 BCHR fountain pen for artists who are interested in using fountain pens for drawing. In it do a brief overview of the pen, and talk about the advantages and disadvantages of using to to make art.
This is a commonly available, relatively affordable pen that can be bought on Ebay for around 150, depending on the degree of flex and general condition. BCHR stands black chased hard rubber (ebonite). Sometimes these pens come a streak reddish ebonite, which is very attractive, but only serves to make it more expensive.
These pens are sometimes marked 52 1/2 which indicates a thinner pen, or 52V which indicates that that the pen is shorter.
Buying vintage pens online can be tricky. Make sure you're buying from a reputable seller, that the pen is fully restored and ready to write. Otherwise you might receive a pen that needs costly repairs, or is irreparable. Do not rely on the seller claiming that the pen is "flex." If you don't see a writing sample, don't buy the pen (and even then, sometimes those writing samples push the pen beyond its safety zone, or are just plain bogus).
These pens are often considerably more flexible than what we're normally used to (even if you use dip-pens on a regular basis). Using them takes a light touch and a practiced hand. If you're new to pen and ink drawing, spend some time developing your dexterity with stiffer nibs before attempting to use a vintage flex pen. Even then, some of these pens, the highly sought after super-flexible wet noodles, are probably too flexible for most drawing purposes, and are best left to advanced calligraphers.