It was reported at around 8.30am on Saturday June 9, a 60-year-old man was attacked from behind as he walked down Chequer Road, Doncaster.
The suspect attempted to pull his chain from around his neck.
The man fought back and the suspect ran off down the road.
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The man was not injured and nothing was stolen.
Officers have been conducting enquiries to locate the suspect and now with the help of the man have produced an e-fit image.
They are keen to hear from anybody who may recognise the man from the image, or who witnessed the attack.
If you can help information can be reported using the new live chat, online portal on https://www.southyorkshire.police.uk/contact-us/report-something/ or by calling 101.
You can also give information anonymously to independent charity Crimestoppers via their website – www.crimestoppers-uk.org – or by calling their UK Contact Centre on 0800 555 111.