Hi i have a proof 81 s mint set but cant tell is it type 1 or 2 so your help is needed again It is very hard to take a pic of a proof silver coins so i took some of the cent hope this help Dave
that is a type 1. The type two has an upper loop that is more pronounced and it also has a bulbous serif.
The 81-S's are not filled and open. The 81 type I is the same as the 79 type II. Here are the pictures along with a bit of an explanation; http://lincolncentresource.com/San_Fransisco_Mintmark_Styles.html. From what I can make out, the op's coin appears to be a type I.