Any sword can be faked. However the Chinese have developed the art to almost a science.
A common listing is "NCO WWII Sword" or "WWII Japanese Officer's Sword". This is not misleading until you see the following…
There were no brass scabbard Japanese swords produced during WWI (at least not by the Japanese. Any "WWII sword" in a brass scabbard, especially with acid etched kanji, flags, armament numbers on the scabbard or blade are most likely fakes. If you buy one buy it as such. These fakes also do not have a habaki.
A very good reference on fakes and replicas can be found at Richard Stein's Japanese Sword Index
A excellent reference on war swords (Shin-Gunto) in general can be found on Jinsoo Kim's Index. This is an excellent translation of the original, more exhaustive Japanese site by Ohmura Tomoyuku
According to Dawson (1996), only five versions of the Non-Commissioned Officer WWII Shin-Gunto sword were manufactured. However a photo of six variations is shown below.
Some of these swords, down to the arsenal mark, are being reproduced and sold, sometimes as "originals."
Dawson, J. (1996). Swords of imperial Japan, Newnan, GA:
Richard Stein's Japanese Sword Index,