Howdy Geezerattack, I have found that there is not an accurate method to tell whether any given seed is viable or not just by looking at it. I have seen seeds with the outside cracked sprout, and as well, I have had seeds that looked perfectly viable not sprout. since I have been using my own feminized seeds (nanner'ed hermie seeds, no colloidal silver used), I have found that placing the seeds in the freezer for a couple of weeks prior to germinating them, seems to increase the 'sproutage' rate. for the last two grows, I have not had any seeds not sprout, some sprouted quicker than the others, but all did sprout. I now, keep all of my unused seeds wrapped up in baggies, in foil, in the freezer until I need them.
Good luck with Your growing.