I own a Visconti Homo Sapiens Bronze Age lava fountain pen with palladium EF nib. I enjoy it quite a bit even if it doesn't hold that much ink and even if there's no ink window. My nib is single tone but I've read others writing about their 2 tone nib on this pen. Did Visconti fit some of these pens with a single tone nib and others with a 2 tone nib?