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R615 Fountain Pen - The Primes

R615 Fountain Pen - The Primes

Regular price £135.00 GBP
Regular price Sale price £135.00 GBP
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Single mindedly designed to produce beautiful flex lines. Precision engineered to be your pen of choice. 

The R615 is designed to be as simple as possible (but no simpler). The overall form is described by a single elliptical curve and a flat plane. Beauty through mathematics. The flat sections line up to make a roll stop across three components: A Swiss watchmakers’ technique. 

The feed design is fine tuned to bring you two options. An efficient and reliable injection molded plastic feed. And a polymer version should you prefer wetter ink flow.

The center of mass of the pen sits in the brass grip section to allow a neutral balance and better control of writing pressure for flex. 

 About The Primes

‘The Primes’ is a numbered edition of flex nib fountain pens, limited to 47 units. Each one inscribed with a unique prime number. Anodised in vibrant ‘prime number red’ with our signature knurled brass grip section.

This edition celebrates our enthusiasm and excitement for all things geeky and mathematical. And what better number series than the primes: at once simple, yet layered with inscrutable complexity, they have inspired passion in the greatest minds throughout human history, from Pythagoras to Terrance Tao. And they pop up with equal frequency in esoteric fields like topology as they do in practical applications such as modern information theory and cryptography. Seemingly simple questions about them, such as Goldbach's conjecture and the twin prime conjecture remain unproved. And yet, they continue to inspire human thought and fuel progress!


    Everything about The Primes has been carefully customised and curated. The pen ships with a specially inscribed stainless steel flex nib. 24k gold plated. With our in-house polymer feed for uninterrumpted ink flow.

    Our classic packaging tin has also been customised. With a special laser etch. To commemorate this edition.

    It’s all standardised and interchangeable

    We like to chop and change and hack and try. The R615 reflects this philosophy - you can make it your own. All our components are international standard and can easily be interchanged with many leading brands.

    • Jowo Standard #6 Nib Unit - the R615 accommodates Jowo #6 Nib Units.
    • Standard #6 nib - most #6 nibs will fit the R615. But not all, due to different nib curvatures.
    • International standard cartridge converter - we’ve got you covered with Schmidt’s excellent K5 converter. But if you want to swap this out or use cartridges - international standard is the way to go.


    The barrel and cap are machined from high grade 6082 aluminium, and then anodised for protection and durability.

    Our grip section is machined from CZ121 brass and is untreated. It is precision textured with a surface roughness for ergonomic grip. Over time it will age and develop a unique patina personalised to you. We think this is wonderful, but should you want to restore it to the original, all it needs is a gentle polish with any standard brass polish and a clean cloth.


      Length: 150mm

      Length uncapped: 138mm (inc. nib)

      Diameter: 16mm

      Section diameter: 10.5 mm, pinch point 10.25mm 

      Weight: 45.23 gms

      Weight uncapped: 35.20 gms with nib unit

      Materials: 6082 aluminium, anodised and CZ121 brass, untreated


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