I'll play. I have detected fruit jars lids that have disintegrated ?into rusty dust as old as 80 years...but I am sure that the rust was sending a halo effect.
Since pottery was first used for canning..depends on how old your treasure is? In 1858 the first screw top rings were made,before that they were glass lids with metal clamps ?or tin plates that were sealed with wax.
I have seen bottle collectors unearth some old jars from the 1920's with the rusted ring intact...
I dug a crystal Arcade coffee grinder from a cellar hole ?that had been made in 1903. I couldn't find the bottom ?jar until a week later...which I detected ?and the lid was rusted ?,but still detected strong...This was in 2001 and the house had burned in 1918...if that helps