Ooh, thank you - that is very useful.
I realised recently that I have 8 to 10 machine needles stuck in my pin cushion, which means they have been changed because I needed a different type of needle, not because they were old. A very stupid thing to do, since it meant I had no idea what sort of needles they were. However, they are mostly Schmetz needles, so I should be able to work out what they are from the colour coding.