There is also "Conserving": maintaining the status quo from when it left service / before Bubba / flood / house fire got to it.
Rust treated / stabilized, but not refinished.
Woodwork repaired, dodgy polyurethane CAREFULLY removed, re-oiled to original spec. generally NO sandpaper, just a cabinet-makers scraper and MAYBE a light touch with BRONZE wool..
If a "shooter" bore thoroughly cleaned, headspace checked, any "dodgy" firing mechanism parts replaced and CORRECTLY fitted. (Old parts treated with preservative, bagged and tagged for reference).
Check out Mark Novak and his "Anvil" series for a LOT more clues.
Here he is, reviving a Gew 88:
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See also:
And:
For the REAL enthusiast: