For some reason i know not, many things from many brands go under different names in the U.S. only. The Profisix is called that everywhere in the world except the U.S.
I have used several Profisix and Lunasix F meters. Great things, but all of mine have suffered the same fate: the needle would start swinging erratically, going to the right end of the scale, hitting the stop rather violently.
I never found the cause, though it appeared to have something to do with a bad contact. I could get the meter to perform that trick by squeezing the meter, or stop it doing so by doing the same.
The potentiometer connected to the scales is fixed to the top half of the body shell. The rest of the electronics is in the bottom half. The connection between the two is made by a few loose ends sticking down from the top half, hoping to hit some tabs in the bottom half. Suspecting that that might be part of the problem, i soldered wires between the contacts (long enough to still be able to open the thing, of course).
It helped! But sadly, only for a while.
I liked these meters enough to have used a bunch of them though.
I stopped (still have a Lunasix F and a Profisix in a box, 'in reserve') when i switched to the Mastersix. Also a great meter, but mine is showing its age now too.
But i often use a metered prism anyway, and i carry a tiny Digisix too, for when a metered prism woud not be the best thing to use.