WHBM, tonytales, treadigraph, and buttonpushignored --
Thank you very much, each of you, for the fascinating and very interesting replies! No worries about thread drift -- I LOVE learning new things! So sorry I did not reply to your kind posts sooner; been doing other things today, and this is the first time I got around to checking PPRuNe today.
And it pleases me no end that my old memory was correct about DC-4s not being pressurized. I have been fond of saying, "Them suckers weren't pressurized!" about the Aramco DC-4s I flew in as a child -- and I was right! (I knew that an aircraft's service ceiling is not her normal cruise altitude, but I was not able to find the DC-4's normal cruise altitude. 10,000 feet sounds quite reasonable.
My first flight on an Aramco DC-4 was in 1950, from New York (Idlewild) to Gander, Newfoundland (where we stopped for several hours that night because the plane had some kind of problem, and I remember the terminal building was a large Quonset hut, and I ran around the terminal with my sister, and enjoyed that a lot) to Prestwick, Scotland, then to Rome, then to Beirut, then to Dhahran.
Yes, it was quite an adventure! I never got bored during that long trip, which took 3 days, because there was always something to do: look out the window at the clouds and when over land, look at the teeny tiny buildings and roads, and read, and other stuff. Didn't need any IFE - we made out won entertainment. And, anyways, none of the segments were that long, unlike today, where technology has enabled flights that are often 10+ hours long.
IK'm so fortunate to have gotten to travel back then. I reallhy enjoyed that.