Nice that you seem to have a couple of wingnut gun nerd friendly shops to work with...I often think the rest of the world is like Montana, and generally cool with most gun stuff. When I visit elsewhere, I realize just how touchy things like that can be.
"Oh, would it be cool for me to check out for serial matching on the internals?"
"um...ok"
Then I proceed to launch the op rod across the room. That is how I learnt myself about the quality of DB and DP's....the gas tubes and all connecting parts related seem to be particularly suspect to ill fitting....
I have purchased two SKS's out of the guilt of doing silly things that I definately know better about...I skated a receiver cover across a glass display case...as I don't store unloaded guns, I kinda skipped the closing of the bolt thing before you release the receiver cover. DOH!
All goofyness aside, if you could get that DB's Chinese characters, perhaps another city arsenal could be added, the more we look at these goofballs...the more information is gleaned.