It seems that a lot of people are interested in vintage flex pens, particularly Waterman, and for good reason. Waterman, in the first half of the 20th. century, made a lot of beautiful pens with incredibly good flexible nibs. However, these pens are rather pricey and scarce.
The Thorobred, made in the 1930s, is a great, full-size pen. It's made out of gorgeous brown, red-veined celluloid, and has chrome trim. The nib is the same #2 nib that people know and love. This one is extra-fine in width when writing with normal pressure, and opens up nicely with heavier pressure.
This is not the softest nib I've ever used, but it does fall into the "medium flex" category, and can be used for shaded writing. The XF line is great for hairlines! This pen would make a great, affordable "first vintage flex" pen. Contact me if you're interested. Thanks!