I used the clone from ZDMAK just this morning (really!). The visible difference between it and a Klann, that I've borrowed and used in the past, is in the shape of the three "indents" for latching on the lower plate.
The indents on the clone are milled without "steps" leading to the indents. No less safe a design, but a touch more difficult to align, but no sweat if you've used one before.
As to the metal. Mine was fresh out of the case, brand new, and when I was done using it;... there wasn't a scratch in the metal. Didn't run a hardness or composition test on it
but it's obviously very good steel. Is it as good as the steel in a Klann? I don't know, but I have no doubt that if I screw up with a coil spring , odds are it will be "operator error", not the tool's failure.
For $199 (my price) it meant the difference between doing it safely now, everytime, versus mickey mousing occasionally since I did not own the expensive Klann and had to beg, borrow or rent it... and being human, I'd sometimes use a less safe "work around". Now I don't have to because of it's affordability.
Only my experience with it so far, everyone has their own. Not meant as an endorsement, just a report. IMHO & YMMV, Take care.