Last open book exam I had was Military Law!
Had enough exams at School.
Only further study I did was work, which were 'closed book' of course, with minimum pass mark 85%. Never had any problems with those whatsoever.
Studied whilst in Army. Also studied AMEB Speech & Drama, to mid-20's.
Now informally 'study' varying interesting subjects through 'The Great Courses', on DVD.
It keeps 'the little grey cells' working!