Pics courtesy of Alex Huangfu of www.Chinesearms.com

If I am not wrong, this should be a 1930s-40s period "Da Dao" with recently replaced scabbard and handle-grip.

The inset picture is a woodblock print from that era featuring a Chinese Communist mounted soldier with his
"Dadao", rifle and 3 stick grenades. The 4 Chinese words translate as "Victory in the War of Resistance"...

Notice the blade's differentially heat-treated cutting edge. I have received feedback that some of these "Da Dao"
were of qiangang (inserted edge) or sanmei (3 plate) laminated construction. It was also known that "Da Dao"
blades used by soldiers of the Chinese Red Army were forged from good quality steel recycled from Chinese
railway tracks. 

Click on any of the 3 pics to view knife-maker Cold Steel's reproduction of the "Da Dao",
a spring steel non-folded version.