Preservation versus conservation, versus restoration is a complicated issue, about which I have written in other venues with reference to antiquarian timepieces. The issues are especially knotty when it comes to objects like watches or fire arms, etc. whose original purpose was as functioning machines, because preserving functionality then becomes part of the "preservation" debate. (That aspect of the issue becomes most acute when the working life of the historical artifact continues into the present day, as it does with various historically important church organs, or with Stradivarius violins. Concert A was only 400 Hz when those violins were made, not 440 Hz as it is today, so most of the necks have been replaced.) Even in the case of uniforms, the issue of preserving functionality may not be entirely irrelevant.
At one extreme, you have those who quite reasonably argue that all the environmental degradation that has occurred since an item originally was created is now an essential part of its history and should be left alone, lest one risk further confounding the historical record. Coin collectors certainly feel that way. However, coins served their purpose simply by being. They didn't have to function as machines. Similarly, a watch and clock conservator I knew observed that, "No one would congratulate me for having taken the Shroud of Turin to the Dry Cleaner." On the other hand, I am reminded of the controversy which once raged concerning whether to remove the several centuries worth of candle residue that had accumulated on top of (or actually, below, strictly speaking) Michelangelo's artwork on the ceiling of the Sistine Chapel. The subsequent removal of said residue embarrassed the then prevailing expert wisdom concerning Michelangelo's alleged preference for "subtle," "muted" colors. So in that instance, it was necessary to erase a part of the subsequent history of the object in question in order to recover a more important aspect of its history. Then too, as others have noted, certain restorative operations also have preservative attributes, because they arrest environmental attack.
Conservators and restorers not infrequently must prioritize what aspects of an artifact's history are most important to them, and sometimes priorities may conflict.
More later.