If you want to know how it's going to look, why not just sand the flattest face and mist it (with water or DNA or mineral spirits)? There's really no way of knowing until you break through the patina and uneven cuts.
I'd start at 120, 180, 220 or 240, 320, 400. (Sand both X and Y directions before moving on to the next grit just like you would with a pen barrel.)
Once you can see what you've got, you can make an informed decision what to do with it.