The chain measures about 20 inches long, from end to end, and should fit at roughly 19 and 7/8 inches in length, closed. It is approximately 1.585 millimeters, or about 1/16 of an inch, wide. Stamped on the spring ring clasp, "14K", marked, "14K", again on an inline lozenge, and signed with a "BBB over a triangle" maker's mark.
The pendant measures approximately 13/16 of an inch, or about 20.6375 millimeters high, bale included, by just under about 11/16 of an inch, or approximately 17.25 millimeters, wide, and roughly 1/8 of an inch deep. The diamond is approximately 1 millimeter in diameter, for an estimated carat weight of .005 carats. (Included please find a US Quarter in the photographs, for the measurement-challenged and ruler-averse.) The bale opening measures just under approximately 1/8 of an inch, or about 3 millimeters wide. Stamped on the top of the bale, "14K", and signed, "Ma". Signed, "Ma", again, on back of the pendant. Diamond tested with a Mizar DiamondNite.
Combined weight is approximately 4 grams, which includes an insignificant portion of gem weight, of course.
This necklace is in excellent vintage condition, but will likely exhibit the expected light surface scratches to the gold from normal wear. The chain has no kinks or bends, and the clasp works well and holds securely. Lightly cleaned by hand, but it has not been professionally polished.
A very pretty, feminine and sparkly, signed vintage I4K yellow & white gold and diamond filigree openwork heart pendant necklace. This is a beautiful, heavy, chain of much higher than average quality with a sweetly styled, lovely heart pendant you'll want to wear often.