+2 and several other indicators. See http://www.cointalk.com/t93080/ and http://lincolncentresource.com/smalldates/1970Ssmalldate.html
After buying a 1970 S small date proof set to use for comparison, I believe the most appearant imdicator to be the loop of the 9. The small date loop is much nearer to being closed than the large. I mean, side by side it is very obvious. Now that I've seen it, it's the first thing I look at. gary