Just FWIW, an import mark has been required since about 1896. It is usually seen as the "country of origin" (COO) mark, the usual "Made in xxxx", and that was the case for all goods prior to 1968, when the law was changed for firearms to require the name and address of the importer and the caliber.
Those No. 4's were not imported prior to 1968, so they should have the full marking. Mistakes have been made, like the fairly common case of an "ENGLAND" mark on a Savage-made No.4; sometimes the workers just didn't put the mark on, but it was required.