This is a vintage sterling silver number 40 charm. Perhaps it's your 40th anniversary or birthday. The nicest one that I have seen. It measures 5/8" with the bail ring by 1/2" wide and it is marked STER.
Thank you for looking!
Item ID:jfg-002367Gender: Female, Age Group: Adult, Color: Sterling Silver, Size: 5/8" x 1/2"