The items - including four rings, an ornate jewellery box and a locket containing two photographs - were recovered in Castleford in May as part of an ongoing enquiry into burglary offences.
Detectives believe they could have been stolen from anywhere in West Yorkshire or its surrounding counties. Officers have now extended their appeal to North Yorkshire, South Yorkshire, Greater Manchester, Humberside, Lincolnshire, Nottinghamshire and Derbyshire after an earlier appeal in West Yorkshire was unsuccessful.
PC Steve Sayles, from Wakefield CID, said: “Despite our earlier appeal to find the owner or owners of this distinctive jewellery, no-one has come forward. This recovery is part of an ongoing investigation into a number of burglaries and we are keen to speak to whoever they belong to.
“We now think that these valuables may have come from outside West Yorkshire. We also think they could belong to an older person who may not realise that they have been stolen or that they are missing. We want anyone who may have any information to get in touch with us.”
Anyone with information should call police on 101 or Crimestoppers, anonymously, on 0800 555111.