What are the chances that one of these actually gives repeatable results?
Surprisingly good. It's just a spring and a dial gauge. The former is either broken or working, and as it turns out, for the most part, so is the latter; tests on cheap digital measuring instruments show pretty good accuracy and precision, even when they are carried out by snobs who are trying to justify buying a Mitutoyo
Will the dt swiss calibration chart will apply do you think?
Only if they have exactly copied the DT spring rate, which is less likely than their ability to source a usable dial gauge. You either trust their calibration, or you entertain us all by building a test stand to do your own calibration.
Surprisingly good. It's just a spring and a dial gauge. The former is either broken or working, and as it turns out, for the most part, so is the latter; tests on cheap digital measuring instruments show pretty good accuracy and precision, even when they are carried out by snobs who are trying to justify buying a Mitutoyo