This is Tiffany & Co.'s Diamond By The Yard. It is a beautiful item with SA rank: Polished.
Brand name: Tiffany & Co.
Model name: By The Yard
Size
Chain length: 42 cm (16.54 in) Pendant:
Height: 0.5 cm (0.20 in)
Width: 0.5 cm (0.20 in): 1.9 g
Accessories
None
Material
750 cm (295.28 in)

Condition Guide:
S: Like new by the store's standards
SA: Almost unused, overall pristine
A: Excellent condition
AB: Great condition, minor signs of use
B: Good condition, signs of wear from normal use
C: Noticeable scratches, dirt, or signs of use
D: Heavily damaged or in need of repair
Item with difficulty being called C: