Can anyone advise if all new air cylinders that are supplied with new pistols should be date stamped?

Both my son and myself have bought new Benelli Kite pistols from our local RFD ( one late 2011 and one this year) and there is no date stamp on any of the four supplied cylinders.

My thoughts are that this makes a nonsense of all the talk about 10 year life cycles for these air cylinders, but also that it makes it impossible to age date them in the future.

Does the importer ( and RFD) have any responsibility to ensure that all new cylinders sold either with the new pistol or as a seperate item are correctly date stamped?