https://www.elmundotech.com/2011/09/06/nintendo-3ds-a-second-circle-pad-and-a-new-r2-button-un-segundo-boton-deslizante-y-un-nuevo-boton-r2/
Nintendo 3DS: A second 'Circle Pad' and a new 'R2 Button' | Un segundo botón deslizante y un nuevo botón R2