ideal Daisho would be a pair of swords, long and short (katana and wakizashi) made by the same smith in the same pattern style. The pair should be mounted in identical matching hardware. Everything should be signed and in top condition. It is rare to achieve all of this.
For a martial artist none of the above is essential you have a daisho if you have both katana and wakizashi and can develop your abilities through training with a good teacher. Obviously it’s preferable if everything is a perfect match but life is not always perfect (did you notice) for you nor was it for the samurai
Sheathed Katana in scabbard (saya)
Japanese sword Forging techniques part 1
All steel swords face a basic dilemma: the steel has to be hard so it can be sharpened, but hard is brittle and breaks easily. Many different techniques have been developed all over the world to over come this problem, but among them the Japanese solution – the combination of composite structure and selective hardening – is quite unique. It is surprising how the smiths of old with no modern understanding of metallurgy, were able to develop such a delicate balance
The steel for a Japanese sword is produced from the black, sand-like iron oxide (Fe2O3) called satetsu. To make steel out of satetsu, the oxygen has to be removed, and carbon introduced into the iron. This process is called smelting. In the traditional Japanese smelter, tatara, the iron is in relatively low temperature to produce the raw steel called tamahagane. The colour and texture of tamahagane depends on the impurities of the ore and is thus dependent on place.
The smith carefully goes through the pieces of tamahagane sorting them according to their carbon content. He then hammers them to plates and breaks the plates to smaller pieces.
From these pieces he collects a rectangular block about 7,5 to 12,5 cm a side, and weighing 2-3,5 kilos. (It should be noted that the finished blade weighs only about a half of this. Much material is lost in the making.) The smith wraps the block in rice paper to hold it