I've known for a while that you can get older record sometimes out of tresoar, that is, church records of births/baptisms/marriages/deaths rather than civil registry entries. However, it's been very hit or miss in looking for anyone in particular, because it's almost exclusively patronymics at that point so if you don't know a lot about the person you are looking for you are screwed.
But I got lucky today. I was trying to pry Sjoerd Sybes Veeman's parents out of a death record in the civil registry, and I was having trouble reading his mother's patronymic (first name was obviously Pietje). Sheer dumb luck handed me his parents' marriage record in tresoar, and I knew it was the right people (Boksum? In that decade? Not likely to be two of them), and Pietje's patronymic made sense of the handwriting (Rinnerts -- I was not going to figure that one out on my own).
This is weirdly fun. Pietje is my great-great-great-great-great-grandmother. If I did that correctly. I've been really lucky with AlleFriezen, picking up several parents out of death records that I didn't think I'd ever get online.