Pic of gear and gear box when first opened. Notice those dry gears.
I didn't find the same sharp edges but there was a total lack of lube in there. The only stuff on the gears was black with wear and the cynlder was almost dry. The antireversal latch was lubed with a bunch of black crap. If you get one of these get a gun doc to lube it up. Nice thing is that the spring is not hooked into the piston like on TM's so changing the spring was way easier.
Notice the difference in colour for the trigger assembly and the piston compared to the first review pics. Not sure if it means anything at all. The spur gear had www.gear.net.cn
If you have a hard time getting the shell back together I found that the cylnder head needed to be pushed back while trying to close the box. Changing the spring for a TM stock raised the ROF but I'm not sure how much of that was the gears getting some good lube.
I'm pretty sure that the bushings were metal. The gears stick out pretty randomly from the gearbox but I think that just a bad mold and doesn't affect the performance if shimmed right.
This is from an ECHO 1 MP5-PDW branded on the stock and body.