If I were going to try and save a hammered surface, I'd probably try small brushes in a dremel tool, not the radial ones but the inline type. Fiber bristles with Maas or perhaps something slightly more aggressive ( perhaps very fine lapping pastes) should let you keep the hammering intact to a point. Another possibility might be using those rubber abrasive points. They could be shaped on coarse sandpaper to a small ball point which could get into each hammer dimple but this work would be time consuming. Any sort of larger abrasive pad will simply remove the hammering all together.

Here's what I mean by the rubber points and here is a view of those end brushes which I might add are available in fiber, brass and steel bristles.

Regards

Christian