From what I can tell, there are no markings on the lockplate. The markings on the barrel do nothing to aid in identification. The 1966 date is confusing. Most dates on classic rifles I have seen are on the lockplate or the barrel near the breech.
Perhaps the only way to positively ID the rifle would be to remove the barrel and lockplate from the stock to examine for any markings. However If you are not familiar with this proceedure, you could easily damage the wood, screws or other parts as they are more than likely rusted in place.
I would leave the rifle alone.