I thought all the windows where fixed...so that comes off as a surprise here. Not that's a bad thing.It's only a guess but It looks like it might be an awning window. Can't see from @Benito's photos, maybe he can take a closer look when he has an opportunity.
We have windows that push open as well as mechanical ventilation in our building.I thought virtually all tall towers had fixed windows.
Two open windows. View attachment 582806