This is a very old set, likely dating to the mid 19th century. It carries the inconsistencies of hand manufacture and may have been produced in the Critchlow factory in Leeds, MA.
It was a great deal of work to produce these buttons. Each blank is sliced from the processed nut, lathed to the desired shape, then sent to the dye room for color. It is returned to the lathe room where it is carved to reveal the inner light color. Then off to the drilling room and finally to the carding room.