Gas cylinder question

Ok Guys,I am now stumped!All these Years I was under the impression that WW2 wide base gas cylinders had the dimple behind the stacking swivel,and post war did not,well,I put a gas cylinder up for sale that I thought was IHC,but turns out it is not(sight is),and I was told that it is SA WW2!It has no dimple,or punchmarks on lug.If this is the case what did the dimpled Gas cylinder represent?Here are some pics of the Gas Cylinder in question,and one of a ww2 narrow base showing dimple....






and the dimple behind stacking swivel hole..


thanks for any info Guys.
Ryan

I've always figured from the forums a SA Gas Cylinder had either a punch mark and/or a letter stamped on the bayonet lug or a letter stamped on the barrel ring. Most of my WW2 Garands have these traits. Narrow based GC are a sure thing on WW2 cylinders.