Rifle ID?

[ringo]

By process of elimination, the '94s and '96s are Swedish and the '95s have a 3rd lug notch the bolt sits in. Yours is not Swedish, nor does it have the notch, therefore, it is a '93.

I looked in the receiver, the bottom of the rear is flat

This should measure approx .460". I got out my '93 and my '95 mausers; my '95 bolt (round) works in my '95 and '93, however a '93 bolt (square) only works in a '93. If your quote is correct about the area under the rear bridge of the action being flat, you have a '93. You have the option of either a '93 bolt which would be correct or a '95 bolt which would function and also fire the rifle without harming the shooter provided the headspace is correct!

Take OOOO steel wool and a little gun oil and gently rub the action to see what bluing is left. Pits are pits and they can either be filled with weld and the action reblued, or fill them with a polymer (JB weld) and use a bake on finish. An acid bath (phosphoric acid, naval jelly) will neutralize the rust and also remove the bluing (which is another form of rust Fe3O4), causing a reblue, refinish scenario.

While I was typing this Gil posted, follow his advice on what to do as the costs do not merit restoration.