Looks like it is the Japanese variant, as seen below. Not surprising if it was picked up in China.
http://www.lexpev.nl/grenades/middleeastasia/japan/type98.html
Of course, dummy grenades were used by all WWII armies for training. It may be one of those. Just unscrew the bottom of the handle. If there’s a string there, pull it and you’ll find out in a few seconds.
