The green ink backs were the first produced from 1965-1975 and the black ink backs have been produced ever since. I know there are a few variations of each but I haven't gotten that far in my research! I run the site
http://www.HOFPlaques.com - it hasn't been updated in a while but may help with some questions like this. Also, I do have plans to update it in the near future, I've just been REALLY busy!