Police are appealing for help from the public to identify a person who may be able to assist with their enquiries.
At about 3.40am on October 21st, a woman was allegedly assaulted while travelling on the Newcastle to Central Sydney train line.
The incident occurred at the train approached Gosford Railway Station.
CCTV images appear to show the man is wearing a grey hat with a Macarthur Rams Football crest on the front, black jacket, grey collared shirt and grey hair.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or Gosford Police Station.
Image: Brisbane Water Police Facebook.