The fact that it's such a clean absence is proof of the grease fill - only a liquid could fill a die so perfectly flush. The pressure of striking the first coin after the grease appeared forced any excess grease from the area. It could possibly have stayed in place for a run of quite a few coins.
rm -rf /Reality subst My Own
Catman, Gary Burke, Bigg Fredd, coinguybrian, numismo, Johnny54321 - CCF members emeritus, now part of Heaven's Own Coin Club.Our members sell on eBay!