Can someone give more details about gas fillings in T5 fluorescent lamps?
I know that the classic 4, 6, 8, 13 W lamps have argon fill, but I'm not sure about others.

There are 11, 15 and 16 W lamps which have the same length as 6and 8 W lamps.
And T5 HE and HO. Is the only diffrence in the electrodes or do they have a different gas filling pressure or even a different gas like krypton?
I know that T8 16, 32 and 51 W 'Eco'(Philips name) or 'ES' (Osram name) have xenon as the buffer gas, so maybe energy saving T5 tubes also have something other than argon. Even T5 HE and HO comes in a more recent energy saving version, like Philips Master TL5 ECO 25, 50, 73 W.

Sylvania B3000 Mk5 to Sylvania RoadLED MIDI

The danger of the radium was highly underestimated back then, but the tendency of the radiation to expose the film was quite a strong argument against, I guess. A brief touch of the paper to the dial and the material would be ruined...

Depends on the type of dark room in question :

 - In military applications there was not really "safe light". Any light increases the exposure by some extent, and it would depend on circumstances if it will be noticed by the adversaries and become a target. The glow paint allows seeing instruments and markings only to who is looking at it up close

 - In photographic film processing dark room it's not really possible to do much work in the dark (too many things to be manipulated which don't glow), so a safe light is essential, and with it there is no use to the glow paint

 - In cockpit, monitoring, etc. light in the room is reduced to enable seeing outside in the dark (and not reflections of the inside in the windows), or to reduce eye strain etc. The glow paint helps seeing instruments, but low level general illumination and suitable contrast colors on the instruments may work well too

In many cases phosphorescent paint (which needs recharging) can be a good substitute

Yeah! I’ve been noticing that too! I made a post on Belgian Street lighting and it has about like 700 views which is insane, are there really that many people interested in Belgian street lights? https://www.lighting-gallery.net/index.php?topic=18978.0
Bots are becoming scary now, they are even becoming good at knowing street lights 

Holophane QSS to a TRT Aspect Mini

I recently purchased some 400watt MH gear and would like to know if it’s safe to run the lamp out of an enclosure. I do know that MH lamps have the tendency to sometimes explode apon EOL.

All HID lamps (excluding HPS, as they run at below atmospheric pressure) carry some nonzero risk of explosion. Even mercury lamps. In practice, it is rather minor for a short test run. Be careful with heavily used ones with blackened or bulged arctubes.

Surprisingly, old style high powered MH lamps like 400W multi-vapor tend to run at rather moderate pressures and are less risky than some smaller MH in 20, 35 and 70 watts!

There are open rated lamps having an extra protection shroud around the arctube for the case it explodes, which can be run with a peace of mind openly. Rare in high wattages.

IIRC, dim pink fluorescent tube is due to mercury starving, so only the buffer gas is lit up. On some tubes you may get a purple color too! Yea you can call them weird tubes

that we call dim pink fluoros "weirded out" because no one knows why they do that.

Yes, as long as the lamp is a 4W, 6W, or 8W tube, an FS-5 or equivalent starter should work just fine at any of those supply voltages. I believe the important part is the lamp's voltage, not the main supply voltage, so there shouldn't be a difference.