Sinn Ignored Because . . .
the Sinn appears to be a very nicely made re-issue / commemorative style piece; Minerva has done these as well.
in my experience, regardless of how nice the commemorative piece may be, the enthusiasts want the ones that were actually used, in the original period. study the 1950's / 1960's rally cars, and I expect that you will find that Heuer had 90 percent market share (among the rally teams). There were a few of the Smiths; maybe some Hanharts; but the Heuers were prevalent. So what are these other brands (Sinn, Minerva and Hanhart) commemorating, when they don't have the true heritage / history?
Jeff