The key to the whole deal is whether or not the receiver (even if manufactured prior to the ban) was assembled into a "SAW" prior to the ban.
You may indeed have a pre-ban, if it was assembled as a SAW prior to the ban - but if it was not assembled into a SAW, it makes no difference when the receiver was manufactured. It would still be considered a post-ban.
Now, do the "Boys From Brazil" see it that way ??? ??? ???
A receiver was produced prior to the 1989 ban,
it was assembled and test fired and then disassembled for sale AS A RECEIVER ONLY, wouldn't that make it a bonified pre-ban receiver?