Unless memory fails me, most Burton harpsichords were (maybe are?) kits. Therefore what you get may be rather variable, depending a lot on the skill of the person who put it together. I have also heard -- but have absolutely no first hand knowledge on -- that the original Burton plectrum design was a bit troublesome -- but that there are decent substitutes.
All that said, "historically authentic" is a most dubious term. Just as I would suggest for pianos, but even more so, what counts is: can the instrument which you are looking at produce the repertoire you want to play on it in a way that pleases you? If so, fine! If not, it doesn't matter how historically accurate it may or may not be -- it's not the right instrument for you.