Vintage Puffy Sterling Silver Heart Locket 1930s-1940s

This antique sterling silver heart locket is from the 1930s or 1940s. It has beautiful abstract engraving on the front, and a STER mark on the back. Another faint hallmark can be seen to the left of the STER, but that second mark has mostly worn off and I cannot decipher it. The hinges on the locket are in good condition and it opens & closes without issue. It does not "click" shut, but stays closed on its own nonetheless. This locket has been well-loved and has faint scratches commensurate with its age. It measures about 1.5 cm from rounded top to pointed tip, and 1.7 cm from the hinges to the edge. I see no hallmarks on the accompanying 36 cm silvertone chain.