From what I can see, the medallion in the picture is for a Colt, but I can't make out whether it is for the 1915 Colt Vickers or for a Colt BMG. Pre-WWI, WWI and WWII Vickers tripods for issue guns did not have medallions on the rear leg. Usually the medallions were put on tripods for export contract guns. The Mk IV tripod was first issued in 1906, so it predated the Class 'C' Vickers, which is the common issue gun, by many years, and was used for many different foregin cntract guns. The early class "C" 1908 vickers did not use the MKIV tripod but had a very different tripod.
I have several of the medallions and tripods that are marked Maxim and dated 1916, which were for an export gun. The cradles are also marked Maxim and Mk IV for these tripods, and are bronze.
A tripod that has holes for the medallion can easily be mismatched with the cradle. There are lot of Aussie cradles with Brit tirpods, as well as early or export tripods with later WWII Brit or Aussie cradles.
Hope this helps.
Black River Militaria CII