Searched "Belgium Rattlesnake" book on the Lewis gun and found several types of the Lewis drum pouch. The Japs used a 3-drum canvas pouch with a harness for shoulder carry and all the other canvas items were for 2-drums. Did not see a single drum pouch anywhere in my quick search.
Have the US 6-drum wood carry case and the metal box to carry 8-drums,2-of each 2-drum in the canvas case per side. Apparently there was a single drum pouch made...see post #4...and it was discussed on a Brit web site with photo's of the 3-4 types made,with changes, for WW1.
Never having seen one myself...and apparently no one here has either...the ones I have will be for display with the 1917 carts in museums. I intend to display the 5-guns in the US military inventory as of 6 April 1917 when the US was the last major power to enter WW1. The 1904 Maxim,1909 Benet-Mecier,1915 Lewis gun,1915 Colt-Vickers and the 1917 Browning,all in 30/06. The 1895 Colt "potato-digger' was improved as the 1914 Colt,but most had been issued to National Guard units and calvary units when the Guard was established in 1907 by Teddy Roosevelt as the later machine guns became available.
If anyone has further info,please feel free to add to this thread or give me a PM.