This is one of only 6 Glued Darth Vader large minifigs, made by LEGO themselves.
This one was signed by Dave Prowse (the original actor if you are not a SW fan!) at the Celebration Europe event in London recently. It was featured on athe TV programme, 'Richard and Judy' in the UK, but I missed it :( It was sold on ebay to raise money for charity and made an incredible £1,650 pounds!! (about $3300 USD).
It is approx 20 inches tall and it looks to be about 9:1 scale. It is very cool and I would love one of the other 5!