The famous PUMA Pro of mark - lots of companies talk about the quality of their steel. PUMA proves it. We proof every single PUMA knife blade made in Germany for hardness. If you examine the right hand side of your knife, you will see a small indented dot on the blade. (Show photo of knife with dot circled). this small dot is the "proof mark" from a Rockwell hardness tester. Using a diamond-pointed needle, every blade is tested for hardness. This needle causes the proof mark that is a symbol of a PUMA and is your personal assurance that your knife will deliver the PUMA quality promise. Before we package our knives, we know for sure that they deliver the right degree of hardness. If it does not pass, it does not ship. Steel - the steel used to make PUMA German knives is the best knife steel in the world. The proper amount of carbon makes a knife easy to sharpen and hold a cutting edge, but it also allows a knife to rust more easily unless other Trace elements are added to protect oxidation. In our 440A steel, we add about 1% carbon for a Great edge and about 17% chromium to maintain the Temper but inhibit rust. About 0.35% Silicon is also added to the base alloy to deoxidize the steel and further stabilize the blade. Additionally, other Trace elements such as Manganese, Phosphorus, sulfur, and molybdenum are added to increase the ability of the steel to form an edge and hold it once formed. These Trace elements cause the molecules to align more evenly when cooling to give better structural strength and consistency. This is a more expensive way to make knives, but we know that every knife that Bears the PUMA proof mark really does deliver the promise of the best knife blade in the world.