The apple doesn’t fall far from the tree. I was going through my Grandma’s knitting tools (I have inherited quite a few craft tools from both sides of the family), and found some home made yarn bobbins. My Grandma was an avid knitter and very skilled. It looks like Grandma used the commercially produced bobbin (yellow one on the left in the photo) as a template, and cut the others out of margarine tubs and other thick plastic. Very nicely done.