Does anyone know what the Waterman Charleston is made of? Does it have a brass core?

The Charleston appears to have a metal jacket on the gripping section and a metal (brass?) liner deep in the barrel. The threaded end of the section is metal. Other than the obvious, the remainder of this (sweet and perhaps underrated) pen is plastic (or for those into marketing hyperbole, exquisite and precious resins). If you are thinking of a Charleston, be sure to try the F nib as Waterman's M nibs are quite broad these days.

Mine seems to be plastic barrel and cap. A brass weight stuck down the barrel, which also blocks most international short cartridges. As for the section it appears to be plastic with a large brass inner connecting section. I have a "M" nib, but mine does not appear to be very wide. Closer to "MF" but as always with line widths, YMMV.

Mine also appears to be mostly plastic, but it has a very solid feel. Quite a lovely pen, and usually at a great price. I have an F nib, which writes on the wide side.

Everyone got it right, I think. The plastic is also injection molded and you will often find mold lines on the section and cap of the pen, and occasionally the body.