Do you have pictures of the jig you are using to hold your coin?
On 50 cent pieces, I hold them by hand. For smaller coins, I super glue then to a thin piece of wood, then once cut, soaking in Acetone to release (which gives you a bonus wood piece). Problem with jigs is that they don't support the middle, and as you can see, as in this case, there is very little metal holding that eagle on. For puzzle coins, this approach is especially important. (originally suggested by Oily)
------Randy
