I saw them at the beautiful International Amphitheatre around 1972 or 73, Smoke on the Water just came out. Opening acts were Tucky Buzzard, don't remember them, and Savoy Brown, they were great even though some of them had just bailed to make Foghat.
That was the only concert I ever saw at the International Amphitheatre (I think I saw a rodeo or circus there years before this). What a fucking dump, the acoustics were worse than the Randhurst Ice Arena, that is really bad. It was the first concert I saw with weed, being smoked openly the whole place was a giant dope cloud. It was a great show despite the venue. Ritchie Blackmore was outstanding, really glad I got to see him live.