The incident happened on board a number 26 bus in Tranent at around 7am on Saturday, 2 June 2018.
The victim was left with minor injuries after being attacked and robbed as the bus travelled through the High Street.
Officers believe the man pictured may be able to assist the investigation and anyone who recognises him is asked to come forward.
He is described as around 5ft 8ins tall and of slim build. He has short brown hair and a birth mark on his right cheek. He was described as wearing a grey or green coloured tracksuit.
Detective Constable Bruce Dodds from Dalkeith CID said: “As part of our inquiries we’re eager to trace the man pictured as soon as possible and would ask anyone who can help us identify him to get in touch at their earliest opportunity. Similarly if the man himself sees this appeal then I would urge him to contact us.”
Anyone with information is asked to contact Police Scotland on 101, quoting incident number 1935 of 2 June 2018, or Crimestoppers anonymously on 0800 555 111.
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