Ring-shaped marks like this are usually the result of working in coin-operated machinery that is worn or damaged. Vending machines and coin sorters and counters are typical culprits. Machines that wrap coins up in paper rolls can also do this kind of damage, though I do not know if such coin rolling is commonly done in Singapore.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis