I once bought a 2' round mirror on eBay with a number, maybe 30, tokens and chips glued around the edge of the mirror. Of course I wanted to remove the chips, since some were quite valuable. This is what I did. First I put the mirror into my freezer. I figured that if I had hardened the glue it might release the chips. Several of the chips and tokens came off easily after being in the freezer for a couple of days. You have to have patience here. For the remaining chips, I got a large plastic bin and filled it with water and let the mirror soak in it. Everyday, for about a week, I would test each remaining chip and token to see if it loosened by prodding them. One by one they finally came off. I believe the glue was a white glue that had been attached to these chips for a long time, years. Some of the chips still had glue attached to the surface. I worked with an x-acto knife and magnifying glass to lift the glue off the surface, as slowly and surely as possible.

These were the results.

Many of the chips now had two colors. It seems that the exposed side of the chip reacted to light and changed colors, sometimes very dramatically.

The tokens all had some lasting memory of the glue, a surface discoloration from the glue.

In some of the chips, the glue had penetrated the surface and held on pretty good. It depended on the surface and condition of the chip. These were the toughest chips to clean. Most of the these chips have a discoloration and rough surface from where they touched the glue.

A few of the chips had no visible damage. No discoloration from light, I guess it depends on the color, and no discoloration from the glue.