Actually no, because the insulation resistance of the binding posts dominates. And there is no real need for the the on board PTFE insulators either. The printed circuit board could have been simply divided into two pieces and mounted directly to the binding posts. Air is an excellent insulator. And that way you also get rid of the wire inductance and a number metal-metal connections (source of thermal EMF).
Copper-Copper <0.3 µV/°C, Copper-Silver 0.5 µV/°C. But most important is to minimize the number of joints and make them thermally equal.
I think in this case using exotic materials has been more important than thinking the whole picture and doing the math.
You are right, but these binding posts are also highly insulating, and extremely expensive, as Guido told me.
If you chose a solution with cables which might touch each other, you must use PTFE, or maybe Kapton which is also highly isolating, but may have better dielectric behaviour.
In my lab, I use relatively cheap PVC mantled cables, which have a resistance of 1E10..1E11 "only". This already creates 1ppm error on 10k, if you drill plus and minus cables to reduce noise pickup.
A yes, one important feature of these cables was the thermal resistance between the resistor element and the binding posts.
That also balances the temperature distribution.
This is important, if you use these devices as working standards, instead of leaving them for days in an oven.
Also don't forget, that Dave has got a prototype, only WEKOMM knows how the devices were built nowadays.
Wire inductance and capacitance may be another aspect, but these are generally so low that they do not play an important role during measurements of the resistor. The time constants involved with these parasitics usually are mostly in the µs range.
AC resistance bridges usually are also capable to measure the ohmic part only.
There are other, more disturbing effects, similar category as L,C parasitic, which I will describe later on.. I'm still collecting information & measurements.
Copper easily oxidizes, giving many 100µV/K thermo offset instead.
The junctions were crimped, not soldered, so this problem applies.
Don't know, how silver coating and its oxides behave, maybe better.
But anyhow, if the whole assembly is well thermally stabilized, these offsets vanish, and will also be eliminated by Offset Compensation techniques.
Frank