I hope you enjoy your sword for what it is. I have the same thing. The first sword i owned was my grandfathers, he brought it back from WWII. I had it restored, polished etc. It is a Show sword (with Showa stamp). Economicaly it cost more to restore it than its monitary value, but it did not matter to me as it has sentimental value. An intersting note is - that sword lead me to start learning about swords, 20 years later i own several swords, some 700 years old, I am a director of the Japanese Sword Society of the U.S. So that one sword was the spark that got me going. I encourage you to learn about the sword and carefully care for it, i would not be discouraged that it is not a family sword, or that it is just a "Showa sword".
Mark Jones
p.s. I still own, and enjoy my grandfathers sword