It is impossible to tell any further without having the lamp in hands and measuring it with a calibrated spectrometer. Leak does not show up immediately, sometimes blue/yellow oxidation on the internal leads may be visible (though, some OK lamps show this too, air remaining at processing probably) and lamp burning voltage may be abnormal.

If you do ever get a photo of the replacement, or another ION, I'd love to see.

Unfortunately, I don’t have a picture of the replacement, but I have a picture of one of the ones that was replaced with it? Here it is

I'd love to see a photo of one installed, if that isn't too much of a bother.

Hmm, they are designed and made in the UK, and they do seem to be reasonably reliable. However, I don't think that there is any excuse for this...

https://indolighting.com/product/ion-road/

Yep! The ion road is tragic! I’ve seen it on a road! It replaced a Thorn Riviera I believe, it looks hideous!

Love the price! 450 Shillings 🤣, my math isn’t perfect, but I think that’s about £22 today?🤔

I wouldn't say that that is entirely true, they still are a reasonably reliable lantern, but for an Aussie lantern, they probably would take the crown for being the least reliable.

The Schreder SYLVANIA STREETLED MK 2, From what I know they have an extremely high failure rate compared to anything else that we’ve used in Australia.

They always either glow them or completely fail, they are also the only StreetLed that can flicker as well upon failure.

Hope my readings were accurate. These were readings were from a relatively accurate clamp meter. If you ever get one I wonder if the wattage affects the readings.

So what this means is that HPS CWAs and MH/MV CWAs both operate in the same quadrant of my oversimplified graph. This does make sense, but if they both operate the same way, then how are they different? Because they are almost certainly different. Maybe they are only slightly different and we would need to take more complex measurements? Idk, maybe I will figure it out when I get my hands on one of them.