The armed robbery happened in Church Street at around 6.40pm on Saturday, October 16, 2021, when a group of around eight youths stole the victim’s jewellery.
Police said four teenagers, aged between 13 and 18, have already been interviewed in connection with the robbery 8 months ago.
But detectives are now appealing to the public to help identify some of the suspects captured on CCTV.
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A police spokesman said: “Do you know the males in these pictures?
"We want to speak to them in connection with a robbery in Preston in which a man was threatened with a knife.
"We appreciate that this incident happened a number of months ago but now is the time that we need to ask for your help in identifying the people in the pictures who may be able to help with our enquiries.”