WJ/FBQ-08. It seems to be a PAP (or in its new name, CAPF, China Armed Police Forces) only weapon. It's marked with WJ (Armed Police) in its designation.
Not sure what caliber it is in but it's probably in 37mm for the riot control ammo. Break-open design like the old American M79 from the Vietnam War era. The PLA (or its new name CA, China Army) is working on a side-open design like that of H&K and FNH for their 35mm grenade.
- Timothy Yan