Back in the day, Leo was trying to mass produce instruments, but as there was very little technology much of the process was by hand. So you got some brilliant instruments and probably some dogs started on Friday night and finished on Monday morning ! The good ones survived the rubbish was junked. When the big corps took over quality dived as more of the process was by machine. Modern computer aided construction takes the variations out of production, but may not make great instruments. A good modern made one is as fine and possibly better than a vintage but it's all down to luck, if you find the great old one hang on to it!