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			Those letters are an "s".  It was a style thing.  It was the practice when using hand written letters, to make an elegant elongated 'S', so to sort of carry that practice into print, they used a character  to sort of 'match' that.  
 If you look closely at what looks like a lower case 'f', it really isn't an 'f'.  The horizontal slash does not go through the stem on both sides...only on the left side.  Compare that with the real letter f and you see that is normal.
 
 It started fading out of practice in the late 1700's, and was still in strong use during the Rev War
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