That depends...
In a way, any 'period' alteration has a different level of value than anything done later in time.
A 'lot' of SAAs were plated/engraved after they left the factory, and even more were cut, so our ancestors muddied those waters a long time ago - and they did so because that configuration suited 'them'.
Plating usually had to go somewhere, unless there was a large city nearby - but cutting a barrel, resetting a front sight and recrowning could pretty easily be done by a decent gunsmith, because those men learned to do it as a part of their trade - plus, there was always Mexico, and those shops did a bang-up business in that field.
Modern embellishment is something else entirely - most don't like it - preferring to keep things as close to factory original as possible - but that's a new wrinkle, due to today's fact that 'everything' is collectable, so long as it says 'Colt' somewhere on the piece.
Placing a value is entirely dependent on period originality of the work done, and what it looks like today - no amount of modern refinishing will return a piece to originality - that bird already flew - but 'careful' cleaning and the repair of things like screwheads and worn-out action parts seems to be appealing.
Collectors collect what 'they' want to collect - each has his own criteria for the type of thing he wants to add when they reach for their wallets.
