Back in the times, before the type 147 Fridolin, more normal VW's were used by the Deutsche Bundespost. However they did differ somewhat from what the public could buy. One thing was the distributor: a centrifugal-only cast iron unit called Bosch VJ4BR20. As can be seen in the Bosch paper above, it was introduced on type 1 based post-vans in September 1957.
As mentioned before in this blog vacuum advancenent is only of benifit when cruising on part load. At full throttle it does not give any difference (thus the logic of having centrifugal advance-only in the Porsches and the Transporters, both being used in full-throttle-applications).
A postal car in a rural area see mostly start-and-stop drivning and very little part-throttle cruising. Thus a "centrifugal only" with a rather fast advancement curve would make sense. I don't know anything about the advancement curve of the BR20, but my guess is it's quicker in reaction than the BR8/019. (If it weren't, why bother introducing a new one?)
My question is: has anyone of you reades ever hold their hands on this holy grail of cast iron VW diatributors? I have seen a picture of one, but the owner sold it several years ago. It would be interesting to compare it to the 010 and 019.