My apology if this image has already been posted and discussed here, but I did a quick search and couldn't find it, so let me add it now.
Here we see Senna at the Japanese Grand Prix (Suzuka, October 20, 1991), just after he clinched the 1991 Driver's Championship. It seems that Senna actually wore the 472.513 Formula 1 chronograph while he drove, but perhaps others here can confirm or correct this suggestion. I have seen other photos of Senna wearing this watch during the GP weekend, but this one may suggest that he wore the watch during the race.
What a great photo!!
Jeff