Well, the rifle is a French Berthier (sometimes called a Berthier-Mannlicher or Mannlicher-Berthier because the magazine was designed by Mannlicher), but I don't think that the bit on the side is factory-original (the peep sight on the rear of the cocking-piece is also a later addition). These rifles would have originally been made at one of three French arsenals (Chatellerault, St. Etienne, or Tulle; it'll be marked on the left side of the receiver), but they ended up being surplussed out around the world, including spots in Africa and SE Asia), so who knows what happened after a local gunsmith got their hands on it. It looks to be in the right place to block part of the trigger or sear from moving, but the only way to know for sure is to try it with the rifle unloaded.