What is the best way to determine the age of an instrument, in this case a tenor banjo. A friend has a Bacon banjo , he was told it was made in 1910 but wantrs to be sure. The hide head was manufactured by Leedy Co in Indianopolis, they I believe became Ludwig. The number on the adjustment bar is 7777 - .there are no other markings other than a little brass plate the simply says " The Bacon". Any help would be appreciated.