For example, National Geographic uses special, customized rotogravure presses with customized inks capable of printing metalized and iridescent colors. Before the digital age in 1977 there was the famous issue on Egypt featuring photographs of the hoard from King Tut's tomb.
Well, I am sorry to disappoint you. I went to my old collection and that has no special inks to reproduce metalized or iridescent colors. It is a standard 4 color separation print. (Click to enlarge)
I must say, the print is a bit "low quality" compared to today's standards. The lineature is bigger than the used today and the colors (probably washed out due time) are a bit dull.
(There is a small white space inside each dot of ink on the print, probably this is an indication of some type of flexography used, not rotogravure. I am not sure, this is an assumption)
High-quality printing processes are capable of generating a much greater dynamic range in color, saturation, specularity and other characteristics than is possible for a camera to capture.
No. All this premises are wrong. Not even in today's printing process is true, unless you use a special ink like a fluorescent one that has special capabilities like converting UV light to visible one, no.
Specularity is not about a standard color reproduction but an additional coat you can put over your print to give it a glossy finish.
Yes, you can tweak a file to make it more saturated, contrasted and colorful than the original one, then use a good quality ink on a good quality paper on a good quality machine, but in general terms, any print process has lesser gamut than any RGB one.
There was a system that used additional Green and Orange inks called Hexachrome, that gave an additional push to this color ranges, but it is not used anymore.
But I have not answered your question:
How is photography done for output to high-quality spot color presses?
The answer is: Color profile.
In any kind of conversion between devices/medium you use a color profile.
This gives you (probably not you, but your computer) the information about what is the color range the next device can reproduce.
When you use a profile for a low-quality output, for example, an uncoated paper, the computer will simulate the dull colors, therefore, will show you a dull image.
If you change the color profile to a higher quality output, the computer will render happier colors, because it is simulating the device can reproduce more saturated colors.
Based on these simulations, the photographer can tweak the image on what he (she) sees on the screen to give it the proper flavor.
Any printer service, should provide a specific color profile, but normally they do not do that, so you need to rely on the generic (but standardized) ones, like SWOP or Fogra, in the proper version.
Additionally, there is another color profile about the color space of the photo, instead of using sRGB you should use Adobe 1998 or Adobe ProPhoto.
Yes, rotogravure gives you a nice quality print, but the decision on using rotogravure or sheeted offset, for example, is not given only by it, but about the durability of the print plate.
A sheeted offset can render a very high-quality print but is not cost effective above, let's say 10,000 reproductions. Nat Geo produces a bit more than that.
You can use specialized inks, like aluminum metalized or fluorescent ones, but normally they are added as a separated plate, not used for color reproduction of a photo.
The metallic look of the golden mask is due the light and shadow on the photo itself, arranged in the light setup of the photoshoot.
A metallic ink or a metallic finish (like Hotstamping) actually yes, have an additional characteristic than a still image can not reproduce: the reflections on what the user has around him, this change when moving your object, but this is the same concept as any movement on your subject.