My MCS was also a mid September build. Recently my car had to go in to the dealers to address a 'Recall' matter with the possibility of the transmission oil being to low. Did you have a recall at all?.......and to make the most of the trip, asked them to look at a couple of rattles and to check that the latest software update is applied. The technician said "Well we're up to 39 at the moment"..........after the work was carried out he said..."Yes you have the latest software" So one would assume then....39....39.1 to be exact!!