Janey, I have a needle gauge that came with my older Grover & Baker so that you could know where to set the eye of the needle. Perhaps that is it.
Your needle situation could explain why I found Weed, Domestic (notched) and Wheeler & Wilson needles all in the drawer to my Grover & Baker 9 from 1870. Perhaps they all worked for the those machines! Such cool discoveries!
Suzanne