Buy camel button filler celluloid fountain pen with 14K gold M nib
Parker Duofold Senior Deluxe Streamline Fountain Pen Set (1930s) - Black & Pearl Moderne w/GT, Button Filler, Medium Flexible Nib (Excellent +, Restored) - Peyton Street Pens
How a PUSH-BUTTON fountain pen works - YouTube
Montblanc Meisterstück 25 Push Button Filler Fountain Pen (First Version from 30s)
Filling Mechanism: Button Filler for Sale at the Pen Market