I'll tell you what WE did......... Ripped out the old torn labels as best we could and sploshed over the area with some of what we called GUM ARABIC. It was a sort of browny colour, thin and a bit watery and was called Arabic because it smelled and looked a bit like the residue from a camel drivers jock strap after a 12 hour ride across the Sahara on a hot day. But I digress as I'm prone to do on an overcast Easter Saturday afternoon......
After a few minutes drying, it left a wishy washy coating. Slosh some more of the foul smelling arabic glue onto the back of the label and stick it on. Then slosh some more GUM, Arabic over the whole lot and leave to dry - and for the smell to leave the Armourers shop.