With long wave UV (black light), you just get the indication that it is high percentage lead glass - that is to say, a rather faint bluish tinge.
UV fluorescence is an extremely complicated subject. For example, as you add more lead to a basic glass mix, the blue colour gets stronger, then as you add more and more, it gets fainter again. And the intensity depends upon other things...according to the experts, the final colour and intensity of fluorescence depend not just on the constituents of the glass, but can also be affected by the annealing process, and the furnace gases (!) - hence I am very uneasy about making anything other than generalisations based on UV fluorescence. It is a useful tool, but the 'it's dusky pink, so it must be St Louis' type of approach is a bit optimistic, I feel, to say the least.