The dates for Verner Panton's Vilbert Chair run the gamut, but they cluster around 1993.
He created the chair for Ikea, and it didn't sell for very long--I've seen "six months," "a season," and "a year"--and apparently, it didn't sell very well, either.
As you'd expect from Ikea, it's made out of melamine-coated MDF. I'm not a huge fan, but I find it very amusing to see how Panton fans and modernist furniture aficionados spin a famous designer's commercial failure on the cusp of his resurgence.
One hack design site gets just about everything about the chair wrong in one, short sentence: "IKEA began a Panton revival when they reproduced his Vilbert Chair in 1994."
One Dutch dealer says, "Only shortly Sold as Ikea made the Chair from different Materials as Verner Panton Required."
But the most frequently repeated explanation, is "The design was perhaps too radical for IKEA shoppers and not that many were sold, making them rare to find today."
This chair proved to be too abstract for the mindset of the Ikea clientele..."
Oddly, the Vilbert is not faring much better in its afterlife as a rare, connoisseur's collectible, either. At auction, one sold for $450 in 2002; an unopened Vilbert didn't sell in 2003; six sold for EUR 266 apiece in 2006, two didn't sell for 400 pounds in 2007. Examples for sale online range from EUR275 to EUR450, while the most sensible prices are still in the thrift shop/garage sale range: EUR25 and "Sure, whatever, just take it."