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The legendary "Kaiser Wilhelm knife", better known under the brand name "MERCATOR", has been produced in Solingen since 1867, at that time at the knife and blade forge Indiawerk Heinrich Kaufmann & Söhne.

Since 1995, the Mercator has been made by OTTER, still in Solingen and still by hand.


It takes more than 20 work steps to prepare the Mercator in Solingen, 12 more handicraft steps are needed in my Düsseldorf workshop for the individual patina until the knife is returned to Solingen for final assembly and sharpening in another 20 work steps.



To patinate the brass handles, I use time-honoured patination techniques from the art of sculpture, but also specially devised processes to create new, unusual structures. Each patina looks different, even if the colour is similar, the structures, feel and look differ greatly from knife to knife.


Patina is also not a surface that lasts forever. And that is a very good thing, because with increasing use of the knife, the patina wears off bit by bit and gives the knife its very own character, depending on the intensity of its owner's use.

At first, a few small spots usually flake off, then the edges wear away and the bright brass shimmers through more and more. Friction, grease from the hands and other mechanical stresses thus naturally create an increasingly beautiful patina on the knife.


Even the hartaufhart/Otter logo and the serial number on the side will only become clear or readable as the patina wears. Look forward to it!


Scope of delivery:

In addition to the knife itself, a beautiful leather case in natural or black is included for protection, as well as a small bottle of Ballistol oil to care for the carbon blade.



Two Mercator knives, one of them with a brass handle, have accompanied me for many years, so it seemed only logical to build my favourite knife in a patinated version.

Excitedly, I drove to my appointment at Otter in Solingen in the middle of the first months of the Corona Pandemic 2020. After all, this was not just any everyday knife I wanted to refine, but one of the most legendary knives from the time-honoured „Klingenstadt“ Solingen.

OTTER's Managing Director Frank Rommel was visibly enthusiastic about my idea of bringing the Mercator onto the market in patinated versions, so almost 3 hours of exchange including a tour of the impressive production facility passed before we agreed to start the project together.


Not at all without pride, the patinated MERCATOR (brass handle) is finally a reality and can currently be purchased in 3 versions. Each knife bears the symbiotic "hartaufhart/Otter" logo and is numbered on the side next to the Mercator lettering.


May it, like all my products, accompany you for a lifetime!

MERCATOR patinated - green

VAT Included |
  • Product information:

    Mercator knife with exclusive hartaufhart/Otter logo and serial number.

    Blade length 90mm / handle length 110mm / thickness 7mm.

    Blade made of carbon steel C75

    handle material brass

    Ring for attaching a ribbon


    Scope of delivery:

    Mercator knife patinated + leather pouch + 50ml Ballistol oil.



    About the Mercator knife:

    The Mercator knife is also known as the Kaiser Wilhelm knife. Although it was not originally designed as an army knife, Kaiser Wilhelm's soldiers quickly learned to appreciate the qualities of the Mercator knife. The knife became an important tool at the front. This is where the colloquial name "Kaiser Wilhelm Messer" still comes from today. In both the First and Second World Wars, numerous soldiers swore by this universally usable pocket knife. However, it was never an official piece of army equipment.

    After the Second World War, American soldiers brought the Kaiser Wilhelm knife to the USA. There, too, the pocket knife quickly found great sales. There, however, it gained a rather dubious reputation: from being a practical lifesaver and all-round knife, the Mercator knife became the most frequently used weapon in the notorious Bronx district of New York in the 1960s and 1970s. Today, the Mercator knife is a reliable companion for travel and outdoor activities all over the world. And the robust pocket knife is also a helpful and popular tool in the household, for DIY and crafts.


    About Otter:

    The Otter company was founded around 1840 in a small Kotten - a traditional water-powered grinding shop - at the Königsmühle in Solingen.


    Its name comes from the fish otters that lived on the banks of the streams and rivers in the Bergisches Land at that time. These adorn the products as the company's logo. The pocket knives and fixed blade knives are made in Solingen using traditional methods. The Mercator knife and the anchor knife are particularly popular in the online shop. Even today, the pocket knives and fixed-blade knives are carefully handmade and sharpened. The range includes knives for leisure, household, garden and hunting. Mostly equipped with carbon blades, these have excellent edge retention and are evidence of robust quality - Made in Solingen / Germany.

  • All product photos of this Otter Mercator knife are example pictures! Each knife looks different: Different colour tones, structure and intensity of the patina.


    The photo of the serial number is also an example.

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