AE 40 Reis, 39.5 mm, 26.13 g.
Countermarked issue, 1835.
"40" countermark within a circle, shaded field.
Countermark applied to an 1829 Rio de Janeiro mint 80 Reis, KM #366.1.
The 1835 countermarked issues were authorized to stem the abundance of locally countermarked coppers of widely differing weights, as an effort to standardize the currency. Previously, nationally issued coppers varied considerably in weight, as different mints worked to different standards, depending on their region.
KM #444.1
Coin about VF, the countermark is Very Fine, and shows distinct traces of the "80" denomination beneath.