I bought one from the seller, greatdel, that looks exactly like the first one.
I tested it with distilled water when I first got it and it was already adjusted perfectly.
I've been using it for about 6 months and it's never needed a readjustment yet.
I could never advise anyone to use a swingarm hydrometer after seeing how far off the mark the first 3 were that I tried.
Good luck with yours. I'm sure you'll be loving it as much as I do.