The photos of the construction of the reference and this aggressive self-manifestation of the seller here in the forum reinforces my scepticism, I made up from this exaggerated description on ebay:
" Over a series of years the design has added filtering, noise cancellation, thermoelectric-effect suppression, high-granularity trimming, temperature compensation, dynamic settling, high-accuracy output, low drift, silicon aging, miniaturization, output jitter-damping, resistive balance, safety features, and excellent repeatability."
I don't see any circuit elements on the photos, and I doubt that any of his secret treatments of this reference, may really deliver such a stability claimed.
In contrary, by using simple metal film resistors (obviously), which have big drift parameters, these will hardly give the stability needed, as hard as one tries to compensate that..
As a (real) scientist, I don't believe in magic either, and really being an experimental physicist, I only believe, what I can see and what I can measure.
Therefore, I'm looking forward to get this D-105 into my lab to check the stability of this device!
(The German customs at Frankfurt airport will store that parcel for another 3 weeks, I assume).
OK, concerning the specification, the seller claims 2ppm accuracy, not uncertainty (!) against his 732A, not againt NIST (!).
That only means the reference is trimmed to better than 2ppm difference compared to his 732A.
There's no claim of the uncertainty of his 732A to SI!
Therefore, I truly believe this spec. parameter.
Therefore, the absolute uncertainty may be measured in any external lab, but that may differ from SI Volt apart of the claimed 2ppm.
But I think, that the claimed stability of 0.15ppm/°C and 1.5ppm/1kHrs in operation can be easily verified, my Veltins climate chamber is already waiting.
But I have to suppose from the foregoing arguments, that the reference will fail these claims.
Anyhow, let's see. I'm really curious!
Frank