First of all - welcome. Do we have another new member from across the water? (one direction or the other
Current understanding/requirement is that the booster, master cylinder, cap, bale, attaching nuts, spacer and vacuum valve were all assembled as a unit then painted semi-gloss black then installed as a unit into the cars.
The type of unit may depend on what factory your car was assembled at (one of the reasons we ask everyone to include when and where their car was built