My speculation about the 'engraving' being a property/evidence number is an educated guess, but, not the only possibility.
I have a nice model 1898
Krag rifle that had a previous owner's Social Security # 'electro-penciled' on the Magazine-Gate.
(Marking valuables with the owner's Social Security Numbers was a brief fad in the 1970's, so Police could identify and return stolen property).
Fortunately, the magazine-gate was easily replaced.
Strange things get done to firearms over the years. Usually, we can only scratch our heads and guess.