The Japanese Shirasaya
The shirasaya often confused as a “shirasaya sword” or “ shirasaya katana” was not really a sword at all even though when opened it would reveal a precious katana blade. This all wooden saya flows seamlessly into the handle and is secured with a mekugi pin just like a sword but it lacked any other furnishings including the important tsuba which would protect the samurai's hands during battle. These pieces would not be and were not designed to ever see a battlefield so why were they often found in samurai homes?
The shirasaya was custom made to fit a blade for the purpose of storage or transportation. Many samurai were passed down blades from their ancestors and when not in war they would be undressed and put away for safe keeping. The shirasaya which translates to “white sheath” was designed to tightly seal keeping oxygen out while providing a protective skin around the katana blade. They would often be put on display proudly in the samurai home because they housed a precious family heirloom.
The shirasaya also played another role from the blades conception. Japanese culture puts more emphasis on perfection than many other cultures with the knowledge that it may take a lifetime to achieve. Often a bladesmith who has mastered or in pursuit of mastering his art wouldn't waste time on things like blade furnishings and would devote his entire time to the making and perfecting his blades. It would then be mounted in a shirasaya and transported to another specialist to create and mount the fittings. The shirasaya would keep the bladesmiths work safe and protected until the other pieces were crafted. The katana could then be removed and furnished before finding it's way to the samurai it was built for.
These “swords” have been seen in the hands of many hollywood actors and have been choreographed into a few incredible fictional fight scenes but the Shirasaya was never made for that purpose and would not have been trained to be used as a sword in battle. It makes for great cinema but was not what it was made for; however if a samurai's home was under a suprise attack, It would not be as efficient but it could likely take the place of a properly dressed katana if absolutly necissary.