Watches including Audemars Piguet, Jaeger Lecoultre, Hublot and Cartier were stolen.
Detective Constable Adam Cronshaw said: "This was a brazen robbery while the store was open and busy with members of the public. It was clearly well planned and executed. These men were in and out in less than 80 seconds and were very particular about the watches they selected.
"I am appealing for anyone who knows who is responsible or has overheard someone talking about this robbery - either before or after it happened - to contact us in absolute confidence.
"The clothing worn appears to be brand new and I am also eager to hear from anyone who knows where they may have been purchased or manufactured.
"The offenders will, at some point, undoubtedly look to offload these watches and I would urge people to be mindful of this robbery and again if anyone is approached with a view to buying any of these items to please contact us."
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