I have always wondered what the old Zinc Beryllium Silicate phosphors looked like. How white is it?
Color temp? I would like to see some photos(If they still work!  ).

Until 1949, Zinc Beryllium Silicate was combined with other phosphors to produce every "white" fluorescent lamp color. I have a GE Mazda 20W Daylight lamp from 1941, shown here. It is much dimmer and somewhat less blue than a common halophosphate Westinghouse Daylight. Also note the red afterglow--I haven't seen that with other lamps. Halophosphate has yellow afterglow, triphosphor has yellow and green, and deluxe halophosphate often has little or no afterglow.

I have two GE "White"-labelled tubes from the 1940's: see my photo.

I described the tint as following: nicer than typical halophosphate cool white, the reds look brighter and the overall rendering is better and somewhat pleasant. It also glows for 1 second when switched off.

In other words, it's warmer (3500K) and somewhat more greenish than halophosphate cool white, with a better colour rendering especially in reds and browns. But it still looks like old fluorescent lighting (it's clearly inferior to triphosphors in terms of colour rendering).

There is also less flickering than halophosphates: the "off" periods are not very dimmer than the "on" periods, and the "off" colour is the same (while the "off" periods are yellow with halophosphates, hence somewhat noticeable).

My tubes are dim, about half the standard flux of modern tubes.

Edit: I've added a photo with the tubes lit.

My tubes are dim, about half the standard flux of modern tubes.

Well, that is normal, the efficacy of tubbes of that day was really barely half of the later halophosphate efficacy. In fact it was the main reason for the mainstream to switch to halophosphates and because of that, the remaining beryllium based were banned (as there was no technical advantage - ironically the same mindset resulting into incandescent bans; the tubes still remain poisonous even without the beryllium when broken)