51
Used by 2 peopleen.wikipedia.org ↗
“My absolute favourite fountain pen is a Parker 51, with mine being manufactured some time in the 1940s.”
Aurynn Shaw Interview, DevOps evangelist, giver of talks, writer of software, conference junkie, profes · via Uses This 
“A Parker 51 that was my grandfather's.”
Rob Beschizza Interview, Managing editor (Boing Boing), storyteller, artificer · via Uses This