[Lynn Eades]

Rich. theres no spec in my book so try this. I think the original lining thickness was 3/8" So take the curve of a shoe with no lining. Plot a circle from it, adding 2 x the lining thickness, which should give you a nominal size Something like 15" From this and the unworn lip inside your drum, you should be able to make an educated guess at the original drum dia, and how much might already have been turned from your drums. Probably Richard F. is on the nail when he said it might be original dia. plus wear.