Nana, I'm not sure which part you're looking at, but here's a photo of the one in my (apparently very dirty) 301A...eeek! Don't look too closely!
[ATTACH=CONFIG]479528[/ATTACH]
It looks the same as the one in Arianna's machine.
Arianna, here's the "difference" between my bobbin base and yours. That's my bobbin base on top of your picture, hence the size discrepancy.
The cutouts on the right are the only differences I can see, and I don't think they matter? Your machine is an earlier one, it's possible mine is just a revision.
[ATTACH=CONFIG]479529[/ATTACH]
And here's the part number on the base
[ATTACH=CONFIG]479530[/ATTACH]
Candace, what gives the shaft being out of place away? Am I Looking at the wrong photo?