Piero,
You have a back air filter plate (060815) for a 1968-70 Commando while a 1971 (SS) takes P/N 061694. The tabs are to mount the ignition condenser pack, particularly on the 20M3 models (rear mounted breakers). I'm not sure if the "S" and '70 Roadster (20M3S) used 060815, but certainly the 1971 models should have replaced it with 061694, which does not have those tabs.