I agree with Joules that charts are only helpful for modern shoes and even then only if the manufacturer also made the chart.
I find it's best to give the inside length and width at the widest point by measuring with a soft tape measure inside the shoe. Let it fall in loosely until you feel it hit the toe, put one finger on the tape to hold it in place then with the other hand push the tape into the heel and take the measurement where the sock or insole stops. For ladies or heeled shoes depress the tape into the arch before following it into the heel.
Prospective buyers can then compare these measurements to a similar style of shoe they own that fit them well, or to their own foot measurements, taken by drawing around the foot on paper and measuring the longest and widest points.
You can give the size marked on the shoe, but be aware the sizing can be of the country they were made in, or for export to/sale in, or in the case of some, the country of design.
Pointed shoes often fit 1/2 size smaller, this can vary depending on the angle.
Was your issue with the original shoe size given, or an international conversion may I ask? Because while shoe sizes in each country has not changed over time, conversions between country's systems have.
