Thank you for the visual comparisons.

Years ago it never occurred to me there were different bobbins for different machines, or that it mattered how they went into the machine - I just popped it in and sometimes the machine worked well and other times it was a royal pain. Once in a while I would have a bobbin that would not fit onto the bobbin winder and just thought I bought a cheap knock off. So needless to say, I have a small collection of my own, because it's not in my nature to throw anything away.

My ignorance truly caused for some very frustrating sewing days.

I'd never keep them all straight!

http://i31.photobucket.com/albums/c3...psee42b606.jpg
I think I may be able to guess something about the 2nd one from the right...

#5 from the left (round) bobbins is for a White Rotary.

I have an old Pfaff treadle. Its shuttle is bullet shaped but it loads from the side not the end. Have you ever seen one of these? It is a good thing it came with the machine, or I wouldn't have known what to look for. It also uses a round needle.

Round bobbins, some notes and pics
 

Kind of for my own reference, I use 3*5 cards a lot, for writing down bits of information. So here's some pictures I took, with measurements, and a nickel for reference, and a penny for your thoughts if you see something you see wrong.
[ATTACH=CONFIG]478391[/ATTACH]
Above-Eldredge/National/Westinghouse/Damascus Grand and others.
[ATTACH=CONFIG]478393[/ATTACH]
Above-Sewhandy made by Standard

Round bobbins, some notes and pics Singer FW, 221, 222, 301, & ??
 

Some version of W&W? Apparently Singer's configuration for the vertical rotary bobbin on this was pretty much a "borrowed" design.
[ATTACH=CONFIG]478396[/ATTACH]

Round bobbins, some notes and pics White FR, 43, 77
 

and probably the rest of the early Whites, Kenmores, some Domestics??
[ATTACH=CONFIG]478397[/ATTACH]

I'll add one for Singer Class 15 and Class 66, shortly.