The teenager was travelling on the number 12 bus from Dudley to Oldbury, in City Road in Tividale, when the incident occurred.
West Midlands Police have now released images of two people they want to speak to in connection with the theft at around 3.20pm on Monday, December 7.
A spokesman for the force said: "Do you know these two lads?
"We want to talk to them after a teenager was robbed of jewellery on the number 12 bus from Dudley to Oldbury, on City Road in Tividale, at about 3.20pm on Monday, December 7."
Anyone with information can call West Midlands Police on 101, quoting incident number 20SW/304267R/20.
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org