I like foreign coins, most of this lot were picked up at a coin place in town with a huge bucketful you can paw through. I use a US quarter as a size reference in some spinning photos, but it's not my only option.
The coins on the bottom row are all the same size. From left to right, there's a UK ten pence piece (from 1992, the newer and smaller one), an Indian five rupee coin (1999), a Jamaican ten cent coin (1977), a Canadian quarter (1969), and a US quarter. The next row up is slightly larger, but the Fiji one penny (1965) and the Indian one rupee (1984) are the same size. The Icelandic ten kroner (1996) is slightly larger. Is there an international standard for coin sizes?