Haven't seen that label before Adam , very interesting. Have a couple of the vases - one each in Blue and green. According to the Smithson book - Dartington : The First 20 Years - as recycled range they are actually numbered VA1007 or VA 1008 depending on size. Should also have an etched D to the base.
Good to see someone other than myself is still collecting Frank Thrower - thought Thrower Dartington had died a death recently!