As you can see it is pretty tarnished.
To start with I took a glass 9 x 13 pan and lined it with tin foil - shiny side up. Then I took one tablespoon of baking soda and one tablespoon of salt and put them in the pain on the foil. Then I poured boiling water into the pan. Dropped the tray in and gave it some time. When it came out it was still a little tarnished so I took some toothpaste and water and cleaned the tray with that.
This is how it came out.
I did a little research, and this is a 1940s condiment tray. I can't believe how well it came out!