Depends on the country of origin.
It could mean a number of things. There's no real way of telling without knowing all of the markings on the rifle, and where this marking is placed.
It means the action of the rifle was made by Mauser or copied by someone.
It means your rifle was made in 1938 at the Mauser AG plant in Obendorf. 42 was the code for Mauser- many different firms built the K98.
It means the action of the rifle was made by Mauser or copied by someone.
Where it was made, proof marks, etc..
Need a detailed description of ALL markings, features,etc. in order to answer.
Assuming you mean a Mauser 24/47, use the sight as you would any open rifle sight. The slider on the rear sight adjusts for range- marked in meters.
Define 7mm. Do you mean 7mm Mauser ( a little less than 30-06), or 7mm Magnum, (a bit more than 30-06)
Markings on white gold are normally placed to indicate the level of purity of the gold. Different manufacturers use varied types of markings on their products.
Square top vs round
What is sightin-in a rifle mean?
probably proof markings