Immediately recognizable by the weird magazine layout, this is a French Chauchat 8mm Machine Rifle ( or Fusil Mitrailleur Chauchat-Suterre Ribeyrolle-Gladiator , if you prefer
), described by WHB Smith as '..one of the most poorly constructed weapons ever developed ..recoil excessive and accuracy poor...poor workmanship and design...'. You can't say fairer than that !
At the beginning of WWII, it was in widespread use by both French and Belgian Armies, using both French 8mm rimmed, Belgian .301 and, later in the war, .30-06 US cartridges.