Here’s a subjective question. There is no “right” or “wrong” answer:
Do you believe collector value is strictly bound to factory original condition?
For some folks, the answer is “Yes”. This makes things easy. You can ascertain the condition with a high degree of certainty. And, you can use Blue Books or recent auction results to establish value.
But, is it a definitive way of establishing desirability or even rarity?
Lots of guys here like revolvers modified by King’s Gunsight Co., for example. But, strictly speaking, they are non-original. I’m sure many people dismiss them accordingly. But, they have a degree of rarity, a historical pedigree, and desirability amongst guys that shoot their guns.
The work of certain gunsmiths adds value, when properly documented, to the right customer.
And, what about grips? We all know the original grips are important to collector value. But, for shooting purposes, S&W factory grips, besides, say, Diamond target stocks, aren’t widely held in high regard. Custom grips by famous artisans generally add value.
*There was a recent thread in which a member got a good deal on a used K-38 with aftermarket grips. He lamented the lack of the factory grips. It turns out, his revolver had come with a nice set of Fuzzy Farrant grips! To the right buyer, this is a huge plus! To the uninformed, it was just another shooter-grade gun.
Magnaport did some cool packages, bundling services like porting, plated finishes, custom sights, and benchrest style muzzle crowns.
Often, they’d add their logo to the sideplate.
The right buyers love ‘em and, in fact, “collect” them.
Having said this, I would seek out an already modified 29 rather than modify a vintage piece in fine condition.
PS: the effect of Magnaporting is likewise subjective to the shooter and their technique. I have shot a lot of International style (aka: Olympic) match shooting. I have shot a Magnaported Walther OSP Rapid Fire pistol in 22 Short (this once the standard rapid fire chambering) and can tell you that it was a distinctive aid in keeping the sights aligned while moving shot-to-shot on the five horizontal oriented turning targets.