poison ring
A ring from medieval times that resembles a locket with a storage area. These were used to store poison to slip in someone's drink or food. They are fairly large and decorative with a flip-up top. Also used to store one's sniffable illicit substances. AKA "crack ring."
She leaned over the table and discreetly opened her poison ring over his drink while distracting him with her ample cleavage.