LEAVE IT ALONE!!!!!
You will not increase value by "restoring" it & you'll totally destroy the character that makes it what it is.
As it sits, it reflects the man who carried it, what he liked, and the times it was carried in. It IS legitimate history. It doesn't have the monetary value it would've if it hadn't been altered from its original factory configuration, but it has incalculable "character" value.
Jeeze, man, if you want to fiddle with it please sell it to somebody who can appreciate it for what it is.