Transit Divisional Response Unit officers are appealing for public assistance as they continue to investigate criminal damage at Flinders Street railway station earlier this month.
It is understood offenders trespassed onto the heritage listed clock tower at the station in the early hours of Wednesday, 10 July.
Police were told the offenders graffitied the clock with red spray paint.
The clean-up bill is expected to cost over $24,200.
Investigators are urging anyone who was in the area at the time and witnessed the incident on the famous clock tower to contact Crime Stoppers.
Anyone with information that can assist police with their enquiries is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au