What is your objective, Frank? To become a go-to tech who can regulate levers for others? I would expect that to entail a study of the half dozen or so different levers: Performance, Camac, Loveland, Jordan, Universal, and so on. And you’ll have to ask each customer how old the harp is because if it’s not settled yet they may be wasting money.
A certification body may be connected to a school for luthiers who make harps. You might, however, especially if you ask L&H, end up with the certification body for those who regulate pedal actions, with their discs and forks, a bit overkill for an aspiring lever technician.