Your question brings back memories from a long time ago. In the 40's when I was in the service our mess chief would take an egg in each hand, crack them at the same time on the edge of an insert, open the shells by flexing his hands and dump the contents smoothly into the insert. He could do this at an incredible speed and it was amazing to watch. Eggs come in boxes of either 30 or 60 dozen eggs and he could go through one in short order. Now and then a bit of shell would fall into the insert and he would have to break his rhythm to pick it out -- but mostly it was just grab, crack, dump, grab, crack, dump ----