I (white boy) visited India in the early '90s and brought back a bunch of rolls of half-Rupee coins as souvenirs. Turns out they were the exact same weight and diameter as US quarters (even down to the number of ridges, which makes me suspect India bought a bunch of used US minting machines to make them), so I started using them at laundromats. The exchange rate at the time was 35 Rs to the dollar, so a load in the US that normally cost $1 was costing me less than 6 cents. I do feel bad for the harassment that actual Indian customers probably ended up receiving, although possibly the owners never noticed or cared.
When i used to go to france for my family holiday every year (i live in southeast england so not far) i used to take as many 2p coins as i could because they were close enough to the €2 coin to work in those insert and twist sweet/small toy machines
British coins really seem absurdly overly-beefy for the monetary value they represent. I think it's a way of saving up metal for the next time the Germans need sorting out.
I used to work as a teller and we used to run magnets on every roll of quarters that came in from laundry mats and car washes. While the weight is correct, American coins are never magnetic. Every single time it's the laundry mats that foot the bill.