You might try Tarn-X dip. Should be able to find it at Wallyworld. It come in a brown bottle. If you have to get a little more agressive I’d try Comet and a tooth brush. Painting the blue background should be easy with a steady hand.
I'd use Eagle One Nevr Dull Magic wadding polish. You can purchase it at auto stores, hardware stores or big box department stores. I used to sell sterling silver jewelry and always carried a can or two of it for polishing up tarnished silver. It's also good on brass, stainless steel and all metals requiring a mirror finish.
I've had great results with tinfoil, boiling water and baking soda. Place it in a bowl on top of some tinfoil. Pour boiling water over and add baking soda.
First, water soak and then gentle scrub with a soft bristle toothbrush. Then gentle agitation in liquid sterling silver cleaner from Target. Comes in a maroon jar and says sterling silver on outside of jar. Find in a counter display in Target's jewelry department. His Majesty finds that most coin silver cleans within 15 seconds of agitation. Best of luck!
I'm late to the party, but that's a really nice find! I can only hope to find something like this some day. Instead all I find is the pull tabs that get left behind, or shot gun shells.