[...]

> I have a distributor with the following numbers on it:
>
>          0 237 023 013 (Bosch)
>          025 905 205B (VW)
>
> but my usual on-line resources for telling what this goes to are
> coming up blank.  I believe it's a distributor for a California-model
> air-cooled Vanagon.

No, it is not an air-cooled Cal dist. 79-83.5 is part # 039 905 205C  [0 237
022 009].

Your number starting with 025 leads me to believe it is a water cooled
distributor.
A water-cooled 84-85 1.9 DigiJet engine uses dist. # 025 905 205D
Close but yours is a B......