You’re not getting it.
“In general, experts can usually tell a fake coin from a real one by matching it to other known examples of the same issue. Gold - being so chemically stable - changes little over thousands of years, leaving gold coins difficult to distinguish from clever modern fakes. But silver does change - it tarnishes, acquires deposits, etc. - and these are harder for forgers to imitate. Bronze changes even more; it’s hard to convincingly mimic a patina”.
You don’t want to ‘scrub’ that.
Woosh!!