Generally speaking these little stamp markings are stage inspector marks. That's when the parts are inspected and gauged then stamped before they're passed on to another machining or assembly stage. Best way to tell if it's real is see if it fits a No5 rifle. Even if it's an Indian made one it could be the real McCoy (?) because they made 60,000 for their Sterling SMG's. So is it a fake? The ones made for the tourist or repop trade are made from lesser steel...... so said! Mind you, the grips sometimes look like they've been finished with a machette