Step 1: Find an old CD
Handle the pieces by the edges to avoid unwanted finger prints.
Step 2: Prepare your keepsake
Place your keepsake on the glue and then add more glue on top of it. Use another piece of CD, silvering side on the inside, to sandwich it all together. Press the pieces together to remove air bubbles from the between the layers.
Use a socket to trace a circle on to the keepsake. Cut out the circle with heavy scissors.
Step 3: Clean it up
DO NOT allow the this to get hot. If you do the glue may separate and allow air it between the layers.
Step 4: Make a bottle cap
Once you have one made, drill a hole in the back and use a rotary tool to expand the hole. Leave a small lip around the edge. Roll up some sand paper and run it through the hole to help clean up the circle.
Step 5: Roll the edge over
Place the keepsake into the cap. Hammer the edge of the cap at a 45 degree angle so it rolls over the keepsake. You'll have to butt the cap into a corner. I used a clamp on a work bench.
Sand out any dings. Repolish the entire assembly with polishing compound.