What slides using what master: Master > Layout used by XX slides

How can I find out (quickly and summatively) what slides are using what master layout?

In the example below I have 6 slides attached to particular master layout, I want to move those 6 slides to another master layout that looks almost identical - my story has 100+ slides, so visiting each slide individually and right mouse clicking to see what layout is using is a painful long and drawnout process.