Last century, when I ran Shop 1, at Y/E stocktaking time I had to count the whitemetal track chairpins.
Just as Nigel does later, I counted out a small amount and I then popped into my local chemist with the whole bag. After explaining my madness (and what the castings were for) the weighing was kindly done and the maths applied (not forgetting to add back on the counted-out packet) - Who remembers the little brown packets quite often with a description note in Phil Kerr's hand?
By the way. my old departed car was renowned for being a mobile foot bath as it let in so much water through the baulkhead and into the passenger foot-well. A Ford Puma - obviously! Probably a Friday afternoon model when the caulking stock supply had run out. If you look up the problem on-line there are 25 pages of comments and 25 ways to fix it. I cured it by taking it to the dump!