For your specific question, here is a link that shows what the bull's eye looks like.
Fertile Egg Pictures
https://www.backyardchickens.com/forum/viewtopic.php?id=16008
Although bantam cochin can be very broody, just leaving eggs in the coop will not assure that she goes broody. She will go broody when the hormones tell her to. I would not leave eggs in the coop. They are an invitation to egg eating predators and you raise the risk of an egg getting accidentally broken, maybe teaching them to be egg eaters. Besides, it is still getting cold enough in North Carolina many nights for the eggs to get too cold to hatch if one does go broody.
I'd suggest gathering the eggs every day. The link below talks about storing eggs for incubation, whether it is under a hen or in an incubator. I don't know if gettting more eggs in the nest every day helps a hen go broody or not. If you think it does, you can add a golf ball, ping pong ball, wooden egg, plastic Easter egg, whatever fake egg you wish, to her nest every day to get several and see if she then goes broody. A hen cannot tell the difference in a fake egg or a real egg.
Since she will stop laying when she goes broody, I'd store her eggs every day until I had enough to put under her, then start using the eggs, oldest first. You can write the date on them when you gather them, so you will know which ones are oldest. This way, you'll always have enough fresh eggs ready to go under her.
Good luck!!!
Texas A&M Incubation site
http://gallus.tamu.edu/Extension publications/b6092.pdf
