29 Vacuum tank ?

Unknown

I got what looks like a 1929 Hudson vacuum tank from the Auburn National swap area. This has a vacuum booster on it and was wondering if you sould be able to see thru the vacuum line hole from the engine ? What should be in there that I do not see ? Also the top is a little different with a small tip that comes up with the float. Thanks for any information and can send pictures if needed. Ron