Neil, Markins is made in the Far East. Its Korean and widely believed to be a copy of the B1 from Arca-Swiss in function. Its "sweet spot" marketing term is not a new feature wholly developed by Markins, that is the hallmark of many heads. You are either a locked head person or a slipper. At least thats what I came away with after months of reading and studying this stuff. And I'm not talking about $100 heads here. Last I checked all the better ones were $300-$450 and that includes Far East, European and stateside products. Funny how materials, labor and tooling can be cheaper in many countries yet the price charged is the same as what the perceived market leader charges. Perception is a very powerful tool.
There is this site you might have heard of, Luminous Landscape, just some guys that shoot for a living and write about it. Am I a disciple? Hardly, but in reading about the D800 they were checking out I discovered the reviewer replaced his Markins heads with Photo Clam, another Korean company which markets an exact Markins copy except as he said, theirs worked better and it was much cheaper. Materials, fit and finish were right with Markins with the finish possibly being harder but only time would tell there.
There are other stories too which I ran across while researching. Markins didn't come across any better than anything else really, which is expected - except here. And thats where my question about biased comes in. I don't see that good mix of recommendations and in reading everything I can for the last few months I have looked. You might want to at least acknowledge that there are others making some pretty decent ballheads.