I did a bunch of research and ended-up on a Canadian 1st pressing with a green WB label. Also went through a canadian late-70's pressing that sounded close, but not quite as good and was too noisy for my tastes. You kind of need a quiet pressing for this album because 3 of the tracks are pretty mellow and are unforgiving to noise floor. Anyway, the Canadian 1st pressing I got is quiet and quite good for me. I got it from a store in Montreal that took photos and sent me audio samples.
It's this one I got:
View credits, reviews, tracks and shop for the 1972 Vinyl release of "Black Sabbath Vol. 4" on Discogs.
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I'm sure UK's are the best. US WB 1st pressing green labels are supposed to be excellent too but those were expensive when I looked. If you can find one of those at a good price, go for it. Japanese Vertigo pressings are apparently decent too, but I never saw one that met my standards. Of course, there's the CB 2011 reissue, but that one was going for more than the Canadian 1st pressings when I was looking.