Many have asked about Tobin bronze and if Gibson used Tobin bronze alloy in their pre-war tone rings. I have not personally identified any pre-war tone rings that had the exact alloy of Tobin bronze but then again, I did not find any, repeat any Gibson pre-war tone ring that had the same alloy, however it is probable that they are out there especially if there were some "logical" order to Gibson's manufacturing process from getting the raw castings in from the factory and turning and plating them and by some miracle having them in some kind of sequence of which I seriously doubt.
I do know that Tobin bronze is certainly within the broad spectrum of alloys that have been manifested by analysis by myself and others and John Janzegers apparently though so because he had his tone rings cast from Tobin bronze.
Tobin bronze alloy was used by the US Navy for different shipboard applications and the alloy as follows:
Copper (Cu) 82.67%
Tin (Sn) 12.4%
Zinc (Zn) 3.23%
Lead (Pb) 2.14%
and other small element amounts to round out to 100%.
Janzegers tone rings were very good especially on a pre-war pot conversion and with a good 3-ply wood rim.
I have additional information posted on my website http://www.portercalls.com/aboutus concerning some tone rings that are in the "ball park" of the Tobin Bronze.
Bill Porter