A man was arrested after another male was allegedly punched outside a Lincoln bar in the early hours of Tuesday morning.
The incident happened outside The Original Bierkeller on Silver Street at 2.18am on December 10.
The victim was punched by a man described as white, mid 20s to early 30s, with dark facial hair.
He was wearing a black top with a red logo on the right chest area, which is possibly a Tommy Hilfiger logo, police said. He was also wearing lightly coloured trousers and shoes.
One man was arrested shortly after the incident and police are now appealing for information on the identity of a second man.
Police published a CCTV image of a man on Thursday, December 12, who they believe may have information that will help with their enquiries.
The force did not specify whether the man is a suspect or a witness.
Anyone with information should contact Lincolnshire Police on 101 or via email at [email protected] quoting incident 20 of December 10.
It can also be reported through the independent charity Crimestoppers on 0800 555 111 or online here.