Could be a White Rotary Bobbin for another model than mine.
This isn't the exact bobbin for my White Rotary, but its bobbin is that size. It is not slick, it has groves in the top and bottom. My machine is from the 1940's, but it is the same bobbin as my grandma's 1917 White Rotary treadle.
That is my White Rotary in my avatar.