Pelikan 400 Tortoise with oblique medium nib. This is a vintage Pelikan. The oblique medium nib offers line variation with a fairly narrow nib, since a vintage Pelikan medium is close to the width of a modern Pelikan fine nib.
I think the tortoise binde looks beautiful against the brown cap and piston knob.
The ink is Waterman Absolute Brown, formerly known as Havana Brown. It’s a reddish brown with nice shading.