IMO period professional jeweler engraving can be authenticated, as certain hand engraving in styles of the time are a lost art today. Personal hand engraving for the most part is a matter of faith, personally if it's in a large group of items from the family I tend to believe it is legit. I have two jeweler engraved crosses a 1939 EK 1 and a 1914, I have no doubt they are period jeweler engraved due to their workmanship & style.