Good reading, but... For the "Wilkie" copy, the guy simply didn't realize that the disk itself IS a leveling aid. Also the hairline need to be properly focused first to see the target and the readings simultaneously, that's different from KB-14 he's carrying. It looks like the same principle, but it is not, as you should not bring the eyepiece too close to the eye as required with KB-14, that will create several possibilities to introduce errors.

I'll definitely check the drag (caused by the friction) of mine, however the seller claims it indeed has the sapphire bearing. Also you should never assume it is 0 deg, no matter how "professional" your compass might claim to be, there is no such thing as "zero friction" in physics. You should always pay attention to the needle behavior. A 3 deg drag would be obvious to a naked eye, but I didn't notice anything that bad yet. Also he seem to assume it's 0 for all other compasses reviewed, except the 2 copies on the list (prejudice?).

His "parallax error" is exactly what's caused by the misaligned needle pivot and the dial. On mine it is tested 0. So he's either got a lemon or measured it wrong (e.g. the drag/friction effect could introduce that error being partially compensated by his measurements method). In fact, all you need to amend the drag, when you want the best accuracy, - bring a small ferrous thing to the compass from one side, remove, measure A1, bring it from the opposite side, remove, measure A2, then average the two A=(A1+A2)/2 - good to know trick if you stuck with a really bad compass (typical tech.for non liquid filled compasses of the past, as they were prone to rusting, but in most cases it was possible to disassemble them and polish the post's tip). By the way, a tripod mount will help here a lot again (also by the way: KB-14 has it ).

Oh, and I found the Sight Master, which I've been using, on the list, it's Silva SightMaster. It has a ruler on the side, aiding with the map work. It's strange that the KB-14 seem to have no such a simple to introduce feature (the guy's saying - it's not suitable for a map work). If not a ruler, just a parallel to the sighting line edge would suffice. Could be the specific way KB-14 is calibrated at the factory, though.

So, I would take these "tests" with a grain of salt, as his testing techniques, time of testing, and the subject compasses' history are unknown variables. Nice colorful diagrams are not a sufficient reason to take an action on this data