I want to know the answer to the following question:
In what year was the BS system modified?
All the background I'm provided with is that "The ASA standard underwent a major revision in 1960 with ASA PH2.5-1960, when the method to determine film speed was refined and previously applied safety factors against under-exposure were abandoned, effectively doubling the nominal speed of many black-and-white negative films.". Is that enough to answer the question?
Answer: no