It has been a while since I rebuild a MK-10 but I remember the seats being concave only on 1 side. Are you thinking of a MK-2? or I am thinking of something else?
Some Tabata (TUSA) regulators are just rebranded Scubapro, but you are right a person needs to know the difference.
I would also like to add another brand and that is Sherwood. They are fairly straight forward to rebuild and parts are cheap. They may not be the most loved regulator but when tuned well they breath fine. It is rumored that Scuba.com's
mystery regulator package contains Sherwood regulators.