Since I'm a long time "M" owner, I'll chime in and give my $.02 worth of info about my "M" and how it came.
Mine is a /416\ arsenal, BTC, S. El Monte, CA import, 1994 import. (SN begins with the 94 43***)
Came with a 5 or 10rd Chinese steel magazine. (Too many years of shuffled around to know which one, for sure.)
The only (stamped) numbered parts on my "M" were the Receiver, Bolt Carrier and Bolt, with the Gas Tube and Gas Rod being electro-penciled, albeit almost unreadable. Very poor effort on the part of that worker. I can make out about 2-3 of the 5 digits, (barely, using a little imagination), on either part. The rest of the penciled digits don't resemble any digit. They're original, just penciled poorly. The Stock, Receiver Cover, and Trigger Guard are blank/un-numbered. (Nothing on the Rear Sight Leaf, either.)
The C&A VA BCH, VA import stamp is new to me. I remember the D.I.G. VA BCH, VA importer. Same city, anyway.
*EDIT: I just noticed/figured it out that you went ahead and brought it home. Nice find! Congrats! Looks in great condition. I've used mine a lot and the stock has some dings and scratches, nothing major. The metal is all still good, though. One of my favorite shooters!
firstchoice