s or san francisco mint --makes the proof coin sets --normally their standards are better and often rarer --since a of "production " goes into proof sets -- philly and denver make most of the everday change
This question is specific to the coins you save. You should get a redbook to find out which ones were released for circulation. If you are talking cents "I" would keep all S-mints not regarding wheats that are copper, memorial cents 1968S-1974S were released for circulation but maintain their copper content. All others fall into the proof category. As for nickels, 1968S-1970S were released for circulation and really aren't worth hanging on to. As for dimes and quarters, if they have a S mintmark then they probably were proof at one time and "I" would hang on to them. Same goes for Halves, just be sure you know which dates are silver before you throw an impaired proof back into the wild. Hope this helps and isn't confusing. HH, SE