It was in the first box that the CSO released through their store. That's the one that has the Reiner Prokofiev 5th, I believe. I have a burn job of the Martinon M3. While it's quite good, I certainly wouldn't put it at the top of my list. The performance is fairly fast, generally speaking, which isn't a bad thing for a symphony of that length. The mezzo isn't great at all. Of course, being the CSO, the brass section is the big deal. Guys like Bud Herseth, Arnold Jacobs, Frank Crissifulli (trombone), Kleinhammer (bass t-bone) Phil Farkus (horn) - they were all in their prime back then. Personally, I feel that their woodwinds were somewhat better back then too, but the brass still ruled the roost. The sound isn't the best, but it's good enough for being "live" from the early or mid '60s.
So, how can I put this in context? I think it's much better than the Leinsdorf/BSO M3 from roughly the same period (I think that one is hugely over-rated). I'm also not as big-a-fan of Lennie's first N.Y. M3 as some people are. The early Mahler 3 that I really like a lot is the first Haitink/Concertgebouw one. I think that's from about 1966. From a purely "interpretive" (conducting) standpoint, I certainly think the Martinon one is far, far better than the recent Haitink/CSO one. In my opinion, Haitink was much better at most everything earlier on in his career. The Levine/CSO M3 is definitely slower in the third, fourth, and sixth movements, but it's certainly much better recorded than the Martinon (it was recorded in Medinah Temple). Herseth (posthorn solos) was captured beautifully on the Levine M3 as well. He doesn't sound nearly so good on the Solti/CSO M3, for example.
Hope this helps.