Japanese track iron set Asahi 3mm, 6mm, 12mm, 18mm, 24mm and tow pockets for the irons.
Made from SK5 steel which is a high quality steel and also used in Japanese knives.
Here is a description in English for the steel
What is SK5 steel
SK-5 is the Japanese equivalent of American 1080, a high carbon steel with carbon between 0.75%-0.85% and 0.60%-0.90% manganese. As quenched, it has a hardness near Rc 65 and produces a mixture of carbon rich martensite with some small un-dissolved carbides. The excess carbide increases abrasion resistance and allows the steel to achieve an ideal balance of very good blade toughness with superior edge holding ability. Due to these characteristics, this grade of steel has been used traditionally for making a variety of hand tools, including chisels and woodcutting saws, and has stood the test of time and use over many years in many countries.
For soft woods a bevel of 30 degrees will provide a good balance of performance and durability.
For hardwoods a bevel of 35 degrees provides the best edge durability.
Made in Japan