yousaygo

Hi, I wanted to clean up the inside of my hood tach. So i took it apart, but when i did i noticed that the top cover was only held on by some clear caulking, like it was just stuck on. This does not seem right to me. However, there does not seem to be any visible way to me that the top cover connects permanently to the rest of the hood tach assembly.
I have tried to find some diagrams, i have the 1970 Service Manual and the Assembly Manual and there are no pictures of how the whole hood tach is put together.
So the question is after all this, how does the hood tach cover connect to the hood tach module.
Thanks, Shane