The incident, which took place in the Fantasy Island car park in Sea Lane, was reported this morning at 9.49am.
Gold was being unloaded for a market stall when two men, using a Silver Renault Scenic car, reportedly threatened staff and grabbed the items.
Police would like to hear from anyone who saw the robbery, or anyone who saw a Renault Scenic in the area at the time.
If you can help with the investigation, call 101, quoting incident reference number 110 of 14 October with any information that could assist.
Alternatively email [email protected], putting the reference (incident 110 of 14 October) in the subject box.
You can also contact the independent charity Crimestoppers anonymously on 0800 555 111, or online at crimestoppers-uk.org.