To remove the silvering from a mirror I suggest nitric acid. Not sure
about the concentration but 70% or greater should be fine.

This is unpleasant stuff which will attack almost any metal except gold.
Do the job outdoors since there will be some eye-watering oxides of
nitrogen given off.  The acid can be safely washed away with copious
quantities of water.  It will not harm the glass.

I do not think you will have to resort to the ultimate deterrent of
"Aqua regia". This is a mixture of concentrated nitric and hydrochloric
acids.  It is _extremely_ nasty as besides dissolving any metal,
including gold, it is prone to instability and can start bubbling and
splashing on its own.
--
Jeffrey Borinsky