I had forgotten about British Whitworth, glad you mentioned it. Several years ago, I was working for a company that made machinery, thus there was a machine shop. Once in a while, they would take in machines, not made by them, for repair. Usually machines that no one else would touch. One day, one of the foreman came by my office and asked if I would come look at a machine they were having problems with. None of our bolts would fit. A machinist helper had disassembled the machine and thrown away the old bolts. Gonna replace them during reassembly, but nothing we had would fit, different threads. Found one of the old bolts and none of our thread gauges matched the bolt. Didn't know what we had.
I was told they took the bolt, to the the place where they bought bolts, and they figured out it was Whitworth. Guess the machine had been made somewhere in the UK, but that's just a guess. Last I knew, they were trying to find the correct bolts, instead of having to tap out the holes. Never did find out what they did.
