Are just a porcelain finish inside, so it is real glass.
They were a big improvement over cheaper Was with a galvanized tank that rusted much more quickly.
Premium WHs were either solid Copper or as Dan mentioned Monel metal which is a high copper stainless steel type tank, either of these type WHs lasted almost for ever in addition to being more efficient at heating water.
That washer is the very early version of the new large tub DispensoMat Norge 14/15. TOL and it's the rare bird that has the filter system that's like a F-Flo with filter pan on the agitator. The water level was set to ex-low too, 2 pounds or less. This is the same exact model that's in the POD.
Geesh I'd forgot about porcelain as in the KA dishwashers of yore. Fiberglas struck me as when I had the flood two years ago and was reading up on a replacement there were some models with fiberglass tanks.
When I was a kid, we had an AO Smith gas water heater here, much older than the video one. Now I have my domestic hot water from my oil boiler. I remember seeing AO Smith huge silos in farming country.
My dad's aunt and uncle's house (built in 1936) had a Monel water heater, but they replaced it with a Rheem electric sometime in the late 60's. I think the old one used oil, and they got a gas furnace at the same time, so no longer bought oil.