Nice pics, from the guns mechanism cover on its apparent left side, it's a water cooled Vickers version of the Maxim; the Maxim was original 'Global Machine Gun' used in one licensed form or another by every major power in WW1 TTBOMK.
Browning M1912 (I think - can't remember off the top of my head) the father of the what became the M2/M3 HMG etc, with a Colt Browning M1918 (or M1919?) 'Potato Smasher' in the pictural background