As a further addendum to the discussion at hand, it might prove useful to review the following quote from The Blue Book of Gun Values re Grading Criteria: "...Every gun's unique condition factor-and therefore the price-is best determined by the percentage of original finish(es) remaining, with the key consideration being the overall frame/receiver finish. The key word here is 'original', for if anyone other than the factory has refinished the gun, its value as a collector's item has been diminished, with the exception of rare and historical pieces that have been properly restored. Every year, top quality restorations have become more accepted, and prices have gone up proportionately with the quality of the workmanship..." (italics mine)
As I opined earlier, in most cases concerning refinishing collector grade firearms, it's always safest in terms of value to not alter the original finish in any permanent way. But if one insists on having a collector grade gun refinished, having the factory perform the service is the best way to "minimize any adverse affect on the resale value."