One book that I have found to be invaluable for dating records (at very teals from the standpoint of year) is Joel Whitburn's Pop Memories 1890-1954. While many of the 78 RPM elite look down upon it because they disagree with his methodology of determining chart position for early recordings nonetheless it is an invaluable source of determining the relative popularity of a song. My feeling is that you cannot realy on any one 'chart' to determine popularity, as at least in the USA, you have Billboard and Cashbox along with local radio charts. Even today with no real 'singles' market per se, the chart is nothing more than dice toss as far as I can tell.

Amy