yes, only serial#<136 that is for civilian,
136 are made for civilians. In fact, if this guy is not a dealer or LEO, he's stuck with the rifle and subject to ATF investigations if they choose to.
Yes, there are some unmarked colt A3 tactical out there that with serial#>136, and some dealers selling them to civilians. This is illegal. Even you bought it and ATF didn't knock you, you can't resell the gun unless to another dumb head or pawn shop, since they never ask any questions.