Found this on TheAKforumLLC:
"Now if ya have a serial number in the format of BWA####, BWB####, BWC#### or BWD#### then go buy a lottery ticket as ya have a winner and your gun was made in 1986 through 1989 (A = 1986 B= 1987 C= 1988 D= 1989) the serial number will also be on the front trunion rather than the reciever and it was ASSEMBLED by B-West "C" and "D" recievers may or may not have the rails heat treated but most likely they were as these were assembled by the Smith at Jensens Arizona Sportsman's east store in Tucson, I knew the man and he helped with the destructive testing done earlier and understood the importance of heat treating etc..
Now for those with serial numbers 999#### on the right of the sheet metal reciever or 989### on the left rear then ya have a gun that was built on onea the many many bare recievers or parts kits (chinese parts) sold by B-West these were NOT assembled by B-West and the rails were not heat treated nor were the axis pin holes however they are 1050 steel these recievers were made in 1988 (right side marking) or 1989 (left side marking) they were produced by a sheet metal shop right down the road from B-West.... these recievers were sold for as little as $5 ea even for a couple years after the ATF busted B-West in 1989 there were 417 recievers un-accounted for which the ATF were very upset over not being able to locate
BTW, AKs prior to 1986 were Norinco or other Chinese arsenal built guns which will say "made in china" on them"
Its a BWA serial#, going for $600; has a possible blood stain (probably just chemical) on the receiver, needs re-bluing: