This Eberhard Faber “573″ seems like a predecessor of the modern clutch pencil. It’s 14.5 cm long, with a substantial ferrule and eraser (I wonder, though, what could be done once the eraser was worn down). The diameter is just slightly larger than that of a round wood-cased pencil.
The cap is threaded, and when tightened it holds the lead in place; it was probably a little inconvenient to keep advancing the point. I don’t know what size lead was used, but it looks like the standard 2.0 mm variety should fit.
I’m presuming that most if not all of the barrel is hollowed-out, owing to its lack of weight, but it feels very solid and well-made.