Different LP slicks used in trade magazines

[metal flake paint]

Does anyone know why these were used instead of the released covers (excepting S.U.S.A.)? Were they commercially available or just for illustrative purposes?

[bgas]

I'm guessing you mean, for most of them, without the song titles showing?  If that's the case, perhaps they had to pay less(?) to get the image across ?!?

[metal flake paint]

Yeah, seems plausible. If I were wanting to buy these LPs in the day, I'd be wondering why the record store copy differed to the one that I saw advertised. 

[William Bowe]

I would suggest they tweaked the covers to make them appear more striking in the context of a small picture in a large ad. Most of those covers had a lot of small writing on them and wouldn't have come across well when shrunk down to the size in which they appeared in the ads. I am quite sure they were never commercially available in this way.