The M205 is a demonstrator. The Marine Blue is not: the glossy, translucent plastic of the Marine Blue looks much less transparent in person than in photographs. But the Marine Blue has a definite “ooh shiny” quality.
The M205 is smaller, thinner and lighter, and has the steel nib instead of gold. But it’s also less expensive. And, yet, shiny. I passed this up when it was widely available a few years ago, but as soon as Pelikan reissued it, I snapped one up.
I use modern Pelikans all the time, and with blue my favorite ink color, I’m glad to have both of these.