West Yorkshire Police say they want to help reunite the owners with the valuable items after the men were locked up for a total of 65 years for a string of crimes in Bradford, Kirklees and Leeds.
They say some of the items stolen will be of great sentimental value to their owners.
The appeal was launched after Bradford Crown Court was told of the series of raids by the gang which took place over just two days.
High-performance vehicles were also taken in the eight ‘home invasion’ robberies which occurred in January this year.
Dean Coleman, 47, of Tyersal Road, Bradford, was sentenced to 13 years eight months; Timothy Tordoff, 26, of no fixed address, was jailed for 20 years; Wayne Coleman, 25, of Mary Street, Bradford, received a 15-year sentence; and Yasser Mohammed Nasser, 26, of Broadstone Way, Bradford, was given 6 years and six months.
Police have yet to find many of the items stolen.
They include a 3.7ct marquise-shaped diamond ring and an 18ct white gold and diamond flower design bracelet.
Detective Superintendent Gary Hooks, who led the investigation, praised the victims for helping bring the villains to court and said he hoped people with information about the stolen items would come forward.
He said: “We would firstly like to thank all the victims for their support of what has been a complex investigation, and I hope that today’s sentences will give them some comfort. These significant sentences send a very clear message to those involved in such criminality that they will be harshly punished by the court.
“We are now appealing for the public’s help to trace the stolen items, so we can return them to their rightful owners.
“Some of these pieces are of great sentimental value and we would urge anyone who may have been approached by someone selling these items, or who may have seen them being sold, to contact us.”
Anyone with information is asked to contact DC 5013 Jones at Bradford District CID on 101, quoting crime reference 13160006184.
Information can also be reported anonymously to the independent charity Crimestoppers on 0800 555111.