There is a lot of fail in this thread. I found some references from the ATF itself that show that, without a serial number, the rifle can not be sold without committing a felony.
So, in it's present condition, the value is essentially nothing as both the seller and buyer would be committing felonies if the gun is sold.
Note that the law basically says that if it *ever* had a serial number, then it is a felony to remove that serial number or posses a firearm with a removed serial number. (It's a different situation for guns original manufactured without a serial number from before serial numbers where required. That's not the case here).
Now, there are references to an ATF procedure to restore serial numbers or assign new serial numbers. I'm not sure what makes a firearm elegible for sucha procedure.
Here's a link to an ATF publication and then the relevant text quoted:
As to "Why does it matter?" a Federal Felony is a serious crime. And, one of the goals of The High Road has always been to portray responsible gun ownership and part of that is obeying the firearms laws as written. In my opinion, encourgaging others to commit a felony or saying "that felony doesn't matter" doesn't meet that part of THR's goal.
http://www.atf.gov/publications/download/p/atf-p-5300-4.pdf
(k) It shall be unlawful for any person
knowingly to transport, ship, or receive, in
interstate or foreign commerce, any firearm
which has had the importer's or
manufacturer's serial number removed,
obliterated, or altered, or to possess or
receive any firearm which has had the
importer's or manufacturer's serial number
removed, obliterated, or altered and has,
at any time, been shipped or transported
in interstate or foreign commerce.