Fixing old Duff Mill- how to make the speed indicator work?

Hello all, this is my first post here.

I recently purchased an old DUFF bridgeport style mill and I'm trying to get it ready to go in my shop. I replaced the top bearing and noticed that the speed adjuster wasn't hooked up. I managed to sort that out on my own, but how does the speed indicator tie in? It seems to have not been used in a very long time. The wheel on it has a very narrow range of motion (only covering the range of the numbers on the front plate while covered by the face plate). There is another matching wheel that is connect to nothing, near the shaft that actually adjusts the speed. I feel this is probably related, but... Could anyone tell me how to put this together or what I'm missing?

Here are the pictures.

Imgur: The magic of the Internet

Thanks!

Is the speed indicator disk spring-loaded? If so, my wild guess is that there should be a string anchored to the pulley behind the indicator disk, routed through the pulley under the adjuster shaft and connected to the mechanism adjusting the width of the sheave.

Paolo

That definitely makes sense, but there doesn't seem to be any sort of spring. It just rotates to whatever position you move it and stays there. Maybe I could add a spring to make it work... but I've love to figure out how it is supposed to.
Was this the right part of the forum to post this in? Wasn't sure if Antique or rebuilding.