I don't think it is a rare variety such as the one on the 1943 S Dimes. The S looks like it is what we "lovingly" call A Trumpet S . It has to do with the shape of the lower serif.
The lower portion of the S on that type of S is a little thin and is subject to being weakly punched into the die. It also fills in quite easily. So it is not unusual to see it looking the way it does on your samples.
Thanks,
Bill