The problem about matching canes or lattincino twists as Alan says, is that the workers AND canes moved with the factory - Vasart, Strathearn and even Perthshire paperweights have been found with canes/twists from a previous factory.
Looking at the base of your weight, there are none of the characteristic marks you would expect to see on a PY base. The base of yours is firepolished which means its most likely to be Strathearn but could just be late Vasart. Looking at the very neat setup I am with Alan - early Strathearn.
The dark glass is usually caused by too much decolouriser (manganese or sodium nitrate) being added to the batch. Vasart and Strathearn would not have disgarded a batch of metal just because it had too much decolouriser although I agree that its less common to see dark glass in Strathearn weights.
Hope this helps