Yes, most warping can be eliminated. Remember you are working with clay and plastic. Moisture and heat will soften it so it can be formed again. There is a fine line between softening the clay so the curve can be removed, and wiping out the detail in the mold and smashing the chip into a pancake. It has to be done slowly, a little at a time. I find a stream of hot air on the chip and a flat pice of ceramic tile works best. I use a heat-gun made for shrinking plastic tubing. Heat it for 30 seconds or so and see if it "tinkles" when it is dropped on the tile, If so, keep applying heat till it drops with a dull thud. Then press the chip flat against the tile surface. This works for acrylic plaques as well but you may have to use a clamp or vise to do the flattening because of the large surface. It may not work on the old cellulose nitrate plaques and jetons that have begun to chemically change.

Others have described use of a microwave oven with the chip wrapped in a moist paper towel. I haven't tried this but you will still need some sort of pressure to tell the chip what shape you want it to take.

I recommend you experiment on a couple of inexpensive chips so you get the feel of what is possible before tackling your valuable chip.