You have prompted me to examine mine and from the base rim it also appears to be 3 layers !
Oh, was just plodding through Miller's Collecting The 1960s
and there's a photograph of your lamp in yellow (yours looks lime green on my monitor).
It's Italian, unknown manufacturer, but is apparently borrows
liberally from a design by Italian architect Tobia Scarpa for Flos. Estimate: £120-150.