Detectives say a group of about six or seven men were seen next to two saloon cars parked on the A1035 around an hour before Guest & Philips was raided on Tuesday morning.
Police said the cars were parked in Malton Road, between Molescroft roundabout and Dog Kennel Lane roundabout.
Staff at the jewellers in Saturday Market were threatened with a sawn-off shotgun during the robbery by two men wearing white, forensic- style suits and balaclavas.
They escaped with more than £200,000 of Gucci and Cartier watches in a silver Vauxhall Omega, later found abandoned near Beverley Westwood.
Detective Inspector Mark Chapman, of the major incident team, said: "It is not clear if these are connected to the robbery but we are very keen to identify the men and find out the purpose of them being in the lay-by."
Anyone with information about the group of men or the robbery is asked to call police on 101.
