Tente este link para o driver da Apple CAC SCR-3500 (scmccid_5.0.34_mac.zip) . Mais detalhes nesta página :
Note: There is another SCR-3500 reader being sold now with a Part number different from the original 905141. If you are a Mac user, install this updated driver. Hold the control key [on your keyboard] when clicking the .pkg file [with your mouse], select [the word] Open