How do you tell bobbins that you have acquired fit what machine. I have a featherweight, Janome 10000, an American Home (Made by Necchi I am told) and a Singer (not sure of model). I got a whole bunch of bobbins at an auction with some other things, and am hoping that some will fit at least one or two of my machines, but how do I tell short of trying each bobbin in the machine itself. Can anyone give any advice on that? I have taken a marker and marked on the plastic bobbins with a small dot for my Janome and a letter for the other machine bobbins that I have. It doesn't need to be a big mark, just something you can see and it hasn't affected the sewing in any way.