All too often, bobbins get left in the cabinet and the machine removed and sold/donated. I find it fun when I get a machine/cabinet with the stuff still there - how much does not belong to the current machine. Most often it's for an older machine, so it just got moved along with any other sewing supplies.
My Standard (stout) rotary came with an almost compete set of Singer VS2 attachments.
I looked at a Davis VF machine ones, that came with a full set of Greist attachments - for a rotary zigzag machine.
Right now I have a little gremlin that likes to steal bobbins. He's quite careful about it, except once he gets to the floor, he likes the noise they make and I hear it and retributive them. He's also started stealing pins - very carefully pulls them out of the pin cushion. He also loves playing around the sewing machines - gets up and sits on top of the longarm too. At least he's only unwound three rolls of TP so far.
To the OP - if you post pictures, some of the bobbins are really easy to tell what they are for, and if most of yours are the same, we may be able to figure that out for you.
