Just trying to work out what the point in these actually was. Given how much more expensive than standard filament lamps these must have been, you wonder if anyone ever really purchased them, which probably accounts for the very small production window

I’m guessing it was for life reasons?, it’s well known that low voltage halogen lamps are more reliable in life than their mains counterparts, I think the lumens for a given wattage are better too?

You'd imagine tho that these would have been many times the price than the standard mains version, putting most people off buying them. I mean, we all know the advantages, but I doubt many members of the public buying lamps at their local store would have opted for these? Just like LED now, people tend to buy the cheapest and buy several times and just generally accept stuff has a crap lifespan.

The aim of the game with these was energy saving. If you look carefully there's an IR reflective coating on the inner lamp capsule. A low voltage halogen filament can also be run harder, which also helps efficacy at producing visible light - I think they did manage to get over 20 Lm/W out of these. They came along though just as LED tech was starting to take off and as several folks have said price was always a big barrier so they only had a really short run. An interesting lamp, and probably one of the last real gasps of mainstream incandescent lighting.