Since World War II, many Japanese swords have been mass produced. Replicas and fakes are sold around the world on a regular basis, and many are sold as the real thing. So, how can a person determine whether or not their Katana is the real thing?
Check to see if the blade is made of steel. With many replicas and fakes, the blades are made from aluminum. The easiest way to determine this is with a magnet. A magnet will not stick to an aluminum blade. Also remember, most practice swords (iaito) are made from the lighter aluminum material.
Look to see if you can see a grain in the blade. Because of the forging process, there will be folding marks in the blade. Also look for a true temper line. This comes from the forging process too, and will show traces if specs between the temper line and the blade. Machine made Katanas may have a temper line, but it will be a sleek, uninterrupted line.
Check for serial numbers. If there is a serial number etched into the blade, it is not a true Katana. Of course, these are only a few ways of determining the authenticity of the sword. You should have your sword looked over by an expert in the field.
