Thank you for contacting Mearto with your appraisal inquiry.

It is a beautiful vintage/antique pendant. Such antique jewellery are being offered at auction on a regular basis.
The shape of the heart and the design with the hanging stone is a lovely classic design. Despite its age it is still fashionable and very trendy. Hearts never seem to go out of fashion.
The necklace is made of sterlingsilver, and the stones are probably diamond cut semiprecious stones. It is hard to tell from the photo. However it is very rare to see diamonds combined with sterlingsilver which is why I am assuming that they are not diamonds. The material used for setting diamonds are usually gold or platinum.
The necklace dates from the middle of the 1900s which matches the information you have that it was given in the 1940s. It is a lovely piece in the presumably original box. However due to the materials it is not the most expensive piece of jewellery. However the design is lovely.
The appraisal is conditional as I am not certain about the material of the stones.

The estimate provided is for a well-advertised specialised online jewellery auction, where I believe the heart pendant and necklace has the best chance of realising its fullest potential. However, there is no measurement for the sentimental value you might attach to vintage family pendant. Retail "asking prices" can be higher and vary.

Please let me know if you have any additional questions. I’m happy to help.
Thank you