Watch List notes:

BRAZIL: Joao, as Prince Regent, 1799-1818, AR 960 reis, 1817/6-R, KM-307.3, struck over Peru portrait 8 reales (assayer JP), light tone, EF-AU, R. Gomes notes that there is an 1817/6 overdate, but gives no further information. A look at the search engines noted only one specimen, thus fairly rare.

Estimate: 280-320 USD