It is a later Monarch pressing mastered by George Piros, specifically an -F/-F on side 1 and 2 respectively (there is a very faint second F following each F). This one is sorta like that double C Zep I I sent you; people are just drawn to it even if the recording is not so hot
Barry Diament's mastering notes and his recollection of George mastering it are somewhere in the Hoffman forum archives. raunchnroll, cassius and Randy W have mentioned it several times on that board as well. Randy W mentions it in his review on Fremer's old Music Angle website. I had the Classic 45 and 33 which are also both superb and one of my favorite Classic Records rock releases, if not my favorite.