When I was in a bank we were asked to dress up in times when BaFin (German SEC) was expected in the campus.

That probably happened the first dozen or so times, until staff got over it. ;)

Not if it was Deutsche: they actually have things to hide and an appearance to keep up.

As I understand it, the bankers and regulators who came around and knew the territory usually dressed down for the occasion (polos and slacks). Asking people to dress up would never have worked at this firm, and the SEC never went past the "investigation" phase anyway, so it wasn't a big deal. People who worked there were never told there were visitors - it apparently was actually a frequent occurrence, but they were using a different conference room that one day.

The guy who handled the regulators wore button-down shirts when they were around, and any traders/engineers who had to talk to them often were told to wear a button-down, but that was it.

People from "real Wall Street" who joined usually had a phase of dressing up before they adopted full casual dress. One person lasted months before showing up in a t-shirt. I kind of assumed that they were all buying new wardrobes during that period, but there may have been a culture shock of sorts.