750 represents the purity in mass of that Gold bar.
It means that it is 75% true Gold (Au), in terms of mass (which
very often translates to a volume much smaller than 75%, because
Gold is so dense).
In terms of Karat, your Gold bar is 75% * 24 Kt (the purity
standard) = 18 Kt.
Italy should be the place where the Gold bar was produced.