The iridesence on IoWSG is more subtle than this - it's almost pearlised rather than this bright shiny appearance.
Kerry Glass was one of Michael Harris' ventures, hence the similarity in some designs, the flame pontil mark and the black triangular labels.
Your Kerry piece is unusual Ross, being in the Tortoiseshell spiral pattern originally developed (actually at Mdina) then used in a more delicate way at IoWSG - most Kerry stuff is in the Heather, Peat and Shamrock patterns, or PWs is the swirled design - though often in a green not seen so often in IoWSG.
The flame pontil mark was used at both Kerry and IoWSG. An interesting anecdote is that at Kerry, they lost the flame pontil mark stamp at some point, so they made a new one - but the flame is reversed.
(Rose I wasn't digging at you - it was a bit of a dig at wfs folk who seem to me to want to attribute all small penguins to being friggers by the masterglassmaker Vicente Boffo)