there is an optional "double glazing" for the E53 - never saw it first hand, usually not an available option on US-spec'd cars... The 4.8 seems to be a euro spec car, so double glazing is a possibility... if you have the last 7 digits of the VIN, i can look up the "as-built" sheet for the 4.8 (and the 4.4, if you wish)