If Armalite says it left the factory as a built up rifle, then that's a safe preban lower.
i was at a gun show looking at a preban colt for 1200 bucks.
i asked another shop owner if he had a serial number list handy to check the # against. He said that the responsibility of the preban status was on the seller and if there was ever an issue with the gun the dealer was on the line not me.
i am a bit more cautious than that, about potentially committing a felony.
10 years from now, who is the BATF gonna hand out the jail time to?
The safest preban SAWs are ones that left the factory as built up rifles. A new in the box "never been assembled" lower with a preban serial number, must have been assembled as a functioning rifle for the preban clause to have legal traction. I have not heard of any cases where the gunowner has been charged with assembling a SAW on a NIB lower.
It is a matter of comfort level.
You may never have to verify the status of a gun, but what if you had to? What would happen if you had a 1993 lower assembled with 1999 bushmaster parts? If the lower left the factory as a stripped receiver, the manufacturer cannot legally certify that the part was assembled on a SAW pre 1994. It is a grey area.
Since George says Armalite confirms his lowers preban status, i would value the assembled lower at 600 - 800 dollars & i would build it up to a functioning gun and document its heritage.
The value of the preban SAW is that the gun can have a collapsible stock, threaded barrel end, flash hider & a bayonet lug. The end user has to determine the value of these parts to his/her gun ownership experience.
HTH
dZ