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The 3 bis in the above pic have a border made up of a "continuous chain of scooped out surfaces," somewhat like a concave hollow of a small saucer. According to my jade seniors(shifus) this scooping out of jade surfaces is a hallmark of Ming period jade.
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Left Pic above shows 2 bis with off-centre holes. The first piece is shaped and carved as a flower while the right item also has a border of scooped out surface plus a centre decoration of a flower. They make nice present day pendants.
Right Pic shows an evolution in style. Instead of the chain of scooped out surfaces of the earlier examples this bi features a continuos chain of pearls. In my jade seniors opinion this is reflective of Qing workmanship and design
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I love collecting these small jade objects and accessories and hope I have not been too off the mark in my descriptions and identification. Otherwise shifus out there may well give me a knock on the head !!