Polishing badges

[Restrikes-ok]

Dear cap badge aficionados

It seems a rookie question to ask but......

I am of the ilk that likes to polish a badge before displaying. I paid what for me is big money ie £26 for a Royal Marines Artillery cap badge.

Ive tried bringing it up with brasso and tooth brush but i'm getting no where with it.

Ive heard soaking in coke-a-cola works. Is this a 'housewifes tale' or is there any credence in it ?

Thanks John


Ps any other polishing suggestions welcome