I had, (but sold) a Stamford self regulating generator similar to the Hoffberg. No VR required. Never used the machine, so cannot comment about its operation. Some models had starter windings as well. Alas, not the case with mine, or I would not have sold it! These were high spec items, production stopped because they were costly to manufacture.
Apparently, Cummins bought the rights to Stamford, and so acquired all the documentation, even on no longer produced generators. An engineer at Cummins searched the archives, and was able to find the manual for these transformer controlled self regulating generators: even including the build sheet for the particular generator s/n that I had.
I do still have the PDF of the manual, some of the information may be relevant to the Hoffberg.
Anyone wanting a copy of this PDF for Stamford model D8 and D11 can PM me, i will forward it along.
Cheers,
Hugh