If you're trying to customize the menu then I'm assuming that you're trying to get a reference to the menu so you can add something to it. If that's the case then you don't need the name. The GUID will work just fine. Also, if you have the GUID of a class you can always look it up in the system registry. The class name according to the registry is esriArcMapUI.MapViewCommandsContextMenu.Dim uid As New UID
uid.Value = "{3846A5B5-D3F8-44CB-BFA3-A5C30F4E535F}"
Dim commandItem As ICommandItem = application.Document.CommandBars.Find(uid)