Mark Hansen wrote:




The airport I'm speaking about is Sacramento Executive (KSAC) (it is not
a TRSA). I didn't say separation of VFR traffic; I said separation between
me (IFR) and other VFR traffic.

That's a class D also. There is no separation between you and VFR
traffic. You'll get traffic advisories but that's it.



can you provide some examples of
IFR services provided by a Class C tower (say, Sacramento Intl, for
example)
that are not provided by the Class D tower

The services will be essentially the same, by the tower. You may notice
delays in getting released IFR, that would be your clue that they do not
have automatic releases with SMF.




Again, I'm just trying to understand what make this Class D a VFR tower.

It's VFR because it's a class D and is within SMF's airspace, run by Norcal.