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Mercator K55K Black Cat Folding Pocket Knife

Otter Messer

Mercator K55K Black Cat Folding Pocket Knife


Brand: Otter Messer
Weight: 75 g         7 reviews
The Mercator K55K is a traditional folding pocket-knife of historic origin, first produced in the iconic knife-making town of Solingen, Germany in 1867. Little has changed from the original design, yet despite being in production now for over 140 years, the K55K is surprisingly modern even by today's standards, exceeding the quality and design of many newer knives. Perfect as a working tool for stalkers and bushcrafters alike, it also makes an ideal gift for collectors of historic knives.

The K55K first gained popularity in the United States following World War II, when returning servicemen brought Mercator knives home from Germany. Since then, the K55K's reputation has grown and grown, with outdoorsmen all over the world discovering its compact size, light weight (only 75 g) and premium build quality. The locking blade is made from Stainless Steel, resulting in a knife that is built to last and easy to sharpen. Ray Mears recommends the RWS Quick Sharp as the perfect sharpener for the K55K.

The knife's unique name originates from the company's founder, a Mr. Kauffmann. Mercator is the Latin translation of 'trader', which in turn is the English meaning of Kauffmann. The model name, K55K, comprises of the founder's initial, followed by the street number of the company's original address – Hochstrasse 55. The second 'K' is the initial of the German word for cat – katze - and the famous 'leaping cat' logo can be found engraved on the side of the handle. Indeed, for many years the knife was simply known as the 'Black Cat', or 'Jumping Cat' by American soldiers.

All folding knives should always be used with caution.

  • Handle colour: Black
  • Blade material: Stainless steel 1.4034
  • Blade length: 9 cm
  • Handle length: 11 cm
  • Blade shape: medium pointed
  • Blade thickness: 3.0 mm
  • Spring material: Carbon steel C75
  • Locks in open position
  • Lock release lever
  • 'Leaping Cat' and K55K logos engraved on handle
  • Nail nick on blade
  • Lanyard attachment
  • Weight: 75 g

  Under UK law, this item can only be sold to persons over 18 years of age. Woodlore will need to verify your age before your order is dispatched and a check will also be carried out upon delivery. This item cannot be delivered to a locker.


  Delivery in 1-2 days within the United Kingdom
  UK Orders placed before 2PM GMT will be dispatched the same working day
  Overseas delivery times will vary depending on the destination

Please note that our offices are closed at weekends, so any orders placed after 2PM GMT on a Friday will not be dispatched until the following Monday.

Orders with a total value over £300.00 will be dispatched free via a next day delivery service within the UK at no extra cost.

Please note that in some instances, orders for heavy items may take an extra day to arrive.

  Overseas deliveries
For overseas deliveries, please refer to the following estimated delivery times:

  • Europe: 3 - 5 working days
  • Rest of the world: 5 - 7 working days


A full refund or exchange will be given provided that the items have not been worn or used, and are returned to us within 30 days of purchase, together with all relative labels and packaging. You are responsible for the cost of returning items.

Please ensure that you include a copy of your invoice, along with an explanation of why you have returned your goods. If you wish to return your goods for any reason, please do so to the following address:

Woodlore Limited
PO Box 3
East Sussex
TN19 7ZE
United Kingdom

Product Reviews

Mercator K55K Black Cat Folding Pocket Knife is rated 5/5 based on 7 customer reviews.

All of our product reviews are from customers with verified purchases.

Overall Rating:


  1 of 7

  Not used it much yet but it seems to be an excellent bit of kit. It's light, feels good in your hand, sturdy construction and sharp, what more could you ask for.  

  Keith Willoughby
1st January, 2024

Rated: 4/5

  2 of 7

  Beautiful piece of kit! This is a very 'clean' looking knife: the design is completely unfussy and I love the timeless simplicity of the riveted handle, with the yellow cat providing a touch of class as well as heritage. I particularly like the way the small knuckle guard serves a dual function. On the one hand, when the knife is open it stops your fingers sliding forward onto the blade. On the other hand, when the knife is folded, it stops the square back of the ricasso snagging on your inside pocket. That there should be something so simple and yet so clever at the same time makes me award Otter many, many points for such a quality piece of metalware. Thanks also to Woodlore for delivering the knife expeditiously. I anticipate having a long and satisfying working relationship with this piece of kit!  

12th October, 2023

Rated: 5/5

  3 of 7

  Nice knife, good quality just what I was looking for, thank you.  

  Michael Farrell
13th December, 2022

Rated: 5/5

  4 of 7

  Have been familiar with these knives for many years, my late father who was a part time lobster fisherman always carried one. I preferred Ventures then Lowen Messers when a trawl fisherman, the quality of the Ventures seemed to wain a long time ago then you couldn't get them and the Lowen Messers still remained quite good but as I have aged 70 now I wanted a lock knife and this was the natural choice for me. Having been a fish filleter most of my working life I have become very familiar with good and bad knives and I reckon these to be well up there among the good ones. thank you for your speedy service and good luck in all your ventures and be safe, sincerely yours Jim Collins.  

  James C Collins
2nd December, 2021

Rated: 5/5

  5 of 7

  Such a solid, well built pocket knife. Timeless design.  

  J S
30th November, 2021

Rated: 5/5

  6 of 7

  I first bought one of these knives in the late 60s when it was not frowned upon for young men to possess a pocket knife, especially if you were a Scout. They are simple, superbly designed and hold a good edge. Over the years they were either lost, given away or just nicked so I was very happy to find that Ray Mears was selling them and bought one a few years ago then, unbelievably, it broke. The spring steel which holds the blade open for some reason had cracked. Hopefully this was very much a one off and I have now purchased a replacement. They are quite simply excellent bits of kit and I would never be without one.  

  Chris Waghorn
25th August, 2021

Rated: 5/5

  7 of 7

  A classic folding knife, this design goes back to 1867 when Kaufmann's produced the original version, which was almost identical to today's version, the key difference is the stamped lettering on the back of the folded handle. In terms of use, this is a very well balanced, light and robust, all round knife. I would suggest it is more suitable for general camp use in a bushcraft situation, you will not be battening with it. Having said that the design is almost unique in the world of classic knives due to its long unbroken manufacturing tradition. Made today by Otter Messer, who took over Kaufmann in the upheaval after WW11, this is a rare opportunity to obtain such a classic knife and I would not hesitate to recommend it for enthusiasts and users alike.  

  Paul Biggs
31st July, 2021

Rated: 5/5

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