Imagine you had a Nina (or a Evil Nina, as it were) or some other watch that had a higher premium for a specific variant. Assuming you had no other provenance to go on, and the serial numbers had 'worn' away, then you never really know that yours was born as the more expensive variant of the watch and not just had the dial swapped later. I've only ever seen the usage on TV shows, but the theory goes that you can recover serial numbers even if they've been 'ground' off or some other similar process to get rid of the numbers with an etching gel/agent. Has anyone ever tried this with the back of a watch case? I imagine its only a temporary reveal but it might give you peace of mind for the long run. Does it cause any other permanent discoloration or effect?

An example of what this actually looks like in real life:
http://www.sirchie.com/catalog/product/view/id/1183/?___store=international_english#.WQ9-UMa2y00

The whole hydrochloric acid mention is a bit unnerving...

 

Yes, it can be done if numbers are stamped on which causes atomic bonds to deform. the method for restoring serial numbers is used in police forensics and it works. however, it is quite invasive and required a certain amount of preparatory work. The solution that is used for this kind of stuff is hydrochloric acid and copper chloride.

The prep is to polish the metal to a mirror like finish and apply solution. the rate of the reaction will be faster in less dense areas so revealing areas that have undergone mechanical stress (hence stamped serial and reference numbers).

an interesting article ...
http://what-when-how.com/forensic-sciences/serial-number/

 

That's for tracing guns etc and no one gives a damn about the damage. Doubt that you'd want to do that to something you cared about.

 

Damn this is freakin cool.