I believe the last digit of the model year was removed when someone drilled a hole for scope mounting and then filled the hole in (probably drilled in the wrong place).  Looks like it was filled with JB Weld or some other metal filler.

The serial number was probably polished off (inadvertently I imagine) when someone was polishing this rifle prior to rebluing it.  It has been reblued as the originals were a dark, mottled grey color caused by oil-quenching during the hardening process.  It is very easy to get carried away when polishing metal with powertools. 

I'm no lawyer or gun rights expert, but I believe that with no serial number that rifle may be illegal to own.  I am pretty sure that it is illegal to sell.

daveboy