These stirrups are made of a nickel alloy
They come from South America - probably Argentina.

This design of stirrup is known as an "estribo brasero" or "brazier stirrup". According to some sources this is because hot coals could be kept in the lower part of the stirrup, but it is more likely that they are named after the shape of a traditional frame.

Their lower parts have pierced decoration in a diamond pattern. 
They have suspension loops which can swivel. The joints are modelled as hands or fists. These stirrups have been used and the loops show some wear.

 There are no maker's marks or stamps.

Dimensions : Maximum Width 5" (14.2cm), height 6½" (16.5), depth of tread 1½" (3.7cm)
Weight : 402g (14¼oz)

Ref : stirrup422