Cool, where did you find these?

Lurking on a shelf at a wholesalers, old stock.

I've just salvaged an older version of this dated 1983, though it only mentions 1800mm 75W tubes, I wonder if there is any difference between it and these? The cat no. is still QV 075 (without the SG245 bit on the end that these have) and the stated winding temperature ratings on the label all seem to match so I can't see there is any difference.
Guessing they just expanded the tolerances on the same ballast in the later ones to perhaps slightly over/under drive lamps either side of the 6ft 75W.

Yes, I always wondered how well these actually drive the different lamps listed, compared to a dedicated ballast for each. Especially the 8' 85w tube...

I can only think it is just cheapening out and using one ballast for all three and having some of them run slightly off-spec, given my 1980's one appears identical but is only rated for 6ft tubes.
I've just been testing it with a 5ft 65/80W tube, and the total circuit wattage is sitting around 85-87W with the ballast getting to the high 70C temperature range, which is expected given the dt of 65C and an ambient temeprature of around 20C, so doesn't really seem to be unhappy from what I can tell.