What's the deal with those tooled leather guitar-soundbox covers? I would think they'd muffle the sound, at least a little bit.

Well, they look nice, and are obviously an expensive luxury, perhaps nothing more than a case of conspicuous consumption (i.e., a "status symbol").

I knew that Elvis had a D-18 early on, and assumed that the D-18 was the guitar that got the leather cover. Of course, it could just as easily be a 28 or any other dreadnaught under all that leather ~ with the cover in place, you don't get many visual clues as to the instrument's features.