Here is a zoomed in picture. I thought that the little bump between the thumb and the book would be an error.
Use this page and see if you can find your variety. Compare your coin to those and see if one matches up. You can also read an opinion on how these came about. I am not positive.
With 72 currently available I never felt the desire to search for them. Check out http://www.lincolncentresource.com/smalldates/1970Ssmalldate.html for more info on ALL the different ones.
