It seems many have the opinion that Zeph tenors were the series 2 and were best between late 40's and late 50's or ... serials up to 378xxx I think it is? I know I had one in mid 300xxx range and it was great! Of course I sold it ... damn there was a severe case of seller's remorse! What's the main changes or differences from a Zeph built a couple of years later ... say around low 400xx range? Pics I've seen show the neck is no longer double socket in the 60's. Was anything else changed in the neck or tube, i.e. bore size? I think the idea that the horns built later are considered "intermediate" is of no matter. I believe that's all cosmetics is it not?