C15 rear wheel question

[BOB M]

Hello

Looking at my rear wheel on the C15 (1959) it come without the spacer (40-6019) between the speedo drive box and dust cover, so I brought one and now find the speedo drive doesn't fit up to the two slots on the hub to make it work. Does it need this spacer? I had a C15 a number of years ago and seem to remember that didn't have the spacer either.

Cheers
Bob M