A mysterious motorist intervening during an attempted robbery could be a key element in recovering the abuser, police said.
A 70-year-old woman was slapped in the face by a man after being told in an alleyway on Forge Road in Port Talbot at 1830 GMT on 18 January.
The abuser was disturbed when a driver rang the horn of his car and shouted.
Detective Sergeant David Connick said: "It was a scary attack."
South Wales police said the witness had rescued the woman, who had managed to hold her bag during the attack, before bringing her back to her vehicle.
"It could have had far worse consequences without the intervention of another member of the public," said Detective Sergeant Connick.
"We sincerely hope that this person will come forward because she may have vital information that could help us identify the attacker before anyone is subjected to such a test."
A spokesman for the force said the suspect was about 5 feet 10 inches tall, was skinny and "smelled strongly of smoke".
He wore a large backpack and wore fingerless gloves and a scarf that covered much of his face.
The alley where the attempt of aggression took place is close to Well Pharmacy and the Sweetmans Bakery.