Atru, I have just found a picture of your lamp in Nigel Benson's book Miller's Glass of the 50's and 60's - a collector's guide - page 56. The book says the technique was introduced by Ercole Barovier in the 1950's and is known as the Coro d'orta and was also used for bowls and vases, but that not all pieces in this style are by Barovier as it was much-copied by other factories.