Great buy!
There have been many hunts over the years. One that comes to mind was seeing this book in the color photo gallery in the Overstreet Price Guide in 1976 (The Spirit of '76) or 1977 (Porky Pig).
I was collecting Marvels at the time, trying to complete my Spidey, FF, Avengers, XMen, Thor, etc. runs.
Buying my first golden age book was still at least a year or more away.
I read DCs as well, but I wasn't looking for any back issues, or to complete any runs (at that time).
I believe this cover made me aware that there were other publishers in the 1930s and 1940s that had vanished in the past, that appeared to be incredibly awesome.
I bought my first Centaur from a Sam Fraser mail order catalog in late 1978 (Amazing Man #15).
About a dozen years later I was able to pick up the one that started it all (Centaur-wise) for me.