How to get a BrepVertex's tolerance?

Is there a way to get a BrepVertex’s tolerance in RhinoCommon ?
I see no method or property for that …

Why do you need this?

To be able to store all the data from a Brep, and then use that data to rebuild the same object.

Any reason not to use the OpenNurbs brep (de)serializer code available via RhinoCommon?

That way we would obtain 3dm binary data, right ?