I'd like to clarify my earlier statement concerning (stretched) as apposed to (compressed) surface metal under the halo.
The best way for me to explain my point is to compare the suface metal to the bellows of an accordion. When it is compressed, the pliable material on the top of each fold is stretched, similar to the skin on top of your knuckles when you bend your fingers. Vern noted the terms, radial surface cracking and longitudinal suface cracking. A crack would indicate a separation of metal which was pulled apart. These cracks will only occur at the crest of a bulge or "pile-up". What you end up with is alternating compression and expansion of a very thin layer of metal on the surface. ALL other metal affected by the stamp will be in a compressed state.
Thanks for your indulgence. Now I feel better... unless I'm wrong.
Mike C.