The possible significance of this find is phenomenal.
In all my searches, online and through reference books, I have yet to find a likeness of Benjamin Franklin on an early button. If this is in fact an image of Franklin wearing bifocals, the historical and collector value will be very substantial.
Based of the style and construction of the button, late 1700's is a very close match, which also correlates perfectly with Benjamin Franklin and his invention of bifocals. An additional point of interest, is that some early spectacles had a small handle at the nose bridge, to provide ease in placement and removal from the nose. This could account for the prominent detail noted above the nose on this particular button. 8)
CC Hunter