This is Open Heart by Tiffany & Co. It is a beautiful item with SA rank: Polished.
Brand name: Tiffany & Co.
Model name: Open Heart
Size
Chain length: 40.5 cm (15.94 in) Pendant:
Height 1.3 cm (0.51 in) x Width 1.5 cm (0.59 in): 3.3 g
Accessories
None
Material
18K

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