The set up you have was a common way to mount a scope and a good way. the zero return is very good.
However, it is an individual mount system, usually to each rifle, on a make it fit basis (vs the Weaver rail system etc that many scopes can be used).
You see that the scope has the "rings" soldered onto the scope body. That makes it hard to fit that scope to another rifle - it may fit another mauser 98, but the soldered on bases would need to be the same height etc.
A scope like that (without the soldered on pieces) is worth about 150-200$ in good shape. They were / are good scopes, but not the best in the world.
The bases have some value, but as they must be fitted by someone who takes the time and knows what he is doing, the parts are worth 20-50$ but the labour is worth $200-400 to fit such bases.
To sell the bases and scope on the market (they need to go together) would get you maybe $250 in total, but in my view they belong to that rifle and should stay there.