Here are some pictures of a nice Eagle "I" button I recently found. I don't have a picture of it after I removed the dirt from it with warm water and Very Light SOFT tooth brush cleaning.
After that it had the typical green crusty spots on it so I soaked it in straight janitorial strength ammonia for about 5 minutes and brush again Very Lightly with the SOFT tooth brush, I did this 2 times to get all the green crust off. The result is the first picture, it looked good wet but when it dried it had a chalky look to it. I put some Naval Jelly on it with a small art painting brush and worked it around front and back, with gloves of coarse. Now with the Naval jelly still on it I took a tooth pick and LIGHTLY rubbed the gold areas until I could see the crud coming off, then rinse and repeat as necessary. The second picture is the finished product, the area around the "I" appears to be white, but that's just the reflection, it's gold.
This worked well for me, your results may vary.
GL