Yeah but I've tried different hammertone paints already and they don't show the hammertone look nor do I have prior painting experience.

Powder-coating is very expensive, and you’d have to find a vendor who would be willing to do something on the novelty side. Not to mention if you get a scratch or some damage to the fixture (which will happen, wear and tear), it is very difficult to correct.

A more logical and cost-effective option is to use the regular off-the-shelf spray paint. @BT25 has good experience doing this with his Silverliner. It’s easier, less expensive, and easy to correct if there’s imperfections or you get any sort of surface damage to the paint.

Yup, early troffers were listed in catalogues as early as the 1940s, typically looking like modern 1x4 troffers but with deeper housings and glass instead of plastic. In some cases they were open or had louvers.
Rest-Glow
Curtis Lighting
Day-Brite 1941
Day-Brite 1947

At the time, most installations using troffers arranged them in long continuous rows and were 1-2 lamps per cross section although a few 4 lamp models were available. Fluorescent luminaires was still a mix between recessed troffers and surface mounted types such as half pipers and louvered fixtures. Various models were made, including ones for long extinct lamp types such as F90T17. These of course were predominately preheat, rapid start would not be introduced until the 1950s. Most building ceilings at the time were typically wire lath and plaster or 1x1 tiled so in most cases troffers were a lot harder to install compared to surface mounted luminaires.   

Modern T-bar ceilings were only patented in 1958 before then tiled ceilings were typically attached using furring strips with screws, adhered on, or was a removable system where the tiles needed to be removed sequentially. The 2x4 troffers designed to fit into a T bar ceiling probably came out in the late 50s as well. By 1960 troffers resembling modern 2x4 troffers were in catalogues.

Troffers have been around pretty much since the beginning of fluorescent, but I think the most common style seen today came out in the 1960s or 1970s.

As long as I have been alive, these fixtures are mainstream in commercial lighting. The original ones I think have 4 f40t12 lamps and 2 magnetic rapid start ballasts and has a plastic diffuser with one ballast controlling the outer tubes and another controlling the inner tubes. I have seen these fixtures in 1980s movies and TV shows, but how long have they been around?

looking at an official manufacturing chart I happen to have for the fill gas and pressures of T5 tubes, only the 24W and 39W HO types are Half Neon filled, the 54W 49W and 80W are still Pure Argon, and I think most of the T5 HO tubes you have looked at have been 54W ones?

(although of course there could still be manufacture to manufacture variation)

There are two 54W T5 HO lamps at my floor at my hostel. My father have two 24W T5 HO lamps in his room. Supermarkets here, used to have 49W, 54W or 80W T5 HO lamps.

T5 low current emergency lighting types : Argon + small amount of carbon dioxide

That's interestin. What function does the carbon dioxide has in these lamps?

If there is 40% neon or neon-helium in argon in T5 HO, why I've never seen a red glow discharges at the ends of them?

looking at an official manufacturing chart I happen to have for the fill gas and pressures of T5 tubes, only the 24W and 39W HO types are Half Neon filled, the 54W 49W and 80W are still Pure Argon, and I think most of the T5 HO tubes you have looked at have been 54W ones?

(although of course there could still be manufacture to manufacture variation)

700-series should still be relatively easy to find in all of the typical places, they were super popular. They haven’t been made in over 10 years though, so supply is limited. You should probably be able to find them online pretty easily, though the prices will most likely be astronomical. It might be worth checking your local small hardware store if you have one, my local Ace still has some GE F32T8/SP41s in stock. As for halophosphate, these are super rare. Sylvania made them for a brief time in the early 2010s in response to a triphosphor shortage, but the bans that took place shortly after meant they had to be discontinued. GE also made deluxe halophosphate F32T8s, those were made for an extended period, so they are slightly more common. But all of these F32T8 halophosphate lamps are pretty rare and are probably not something that could be found on demand.

Finished reassembling a vintage fluorescent desk lamp I started restoring last week.