I didn't measure the diameter of this coin but it wouldn't fit in a 2x2 no matter how I tried. It was double struck hence it was just flatten to a bigger diameter.
Netherlands, 2½ Gulden - Ø 38 mm. Well, at least I think that is my biggest circulation coin. Mine is a different year (image: Dutch Mint) but the same type ... Christian
I suppose that since 1900 the largest circulating coin might be Mexico's 40mm Cuauhtemoc 5 Peso silver coin struck in 1947 and 1948.
Here is another image, from worldcoingallery.com: Or try these (obv and rev), from the Dutch Money Museum. Hope the two links work ... (obverse) http://83.149.77.24:8080/collectie_2/FMPro?-db=koninkrijk.fp5&key=33936&-img (reverse) http://83.149.77.24:8080/collectie_2/FMPro?-db=koninkrijk.fp5&key=33937&-img Christian
According to what you wrote, it is from Bolivia. The coin in the second post is from Russia, featuring Empress Anna. Denomination is probably 1 ruble, but I'm not sure about that ... Christian