[Arran]

There is a luxury hotel in Victoria B.C that had it's own power plant up at least until the 60s, it produced 110 VDC so the rooms never had any TV sets up until that time. It was owned by Canadian Pacific who also owned a railroad and it's own steamship line, the steamship terminal was just across the street.
Someone on the alternative forum mentioned working in a building that had DC outlets on the premises. I don't know if they still do but he mentioned testing out an AC/DC set just for laughs and it behaved pretty much as Brenda Ann summarized. There were some Philco models that were DC mains only, not battery, they were series string, with a large ballast, and did not have a rectifier tube.
I think that the fact an AA5 could run off of DC mains was more of a marketing ploy then a practical feature, even in the 1930s, as the market was fairly small. The real innovation was that they could build a cheap set mass market set with no power transformer.
Regards
Arran