I only noticed one old painting of the rose, Redoute's, in the thumbnails, but if you look at the thorns in that painting, something doesn't fit. Either the painting's off, or the thorny RdR of 1823 has been replaced by something a little different. Two of its color sports have supposedly survived, and both are thornier, but the identity of both of those are also disputed.
Rose du Roi of commerce is a fine rose, though, whatever its identity.
<update, five years later>
I noticed that the thorny rose painted by Redoute was labelled Quatre Saisons Lelieur originally, but then marked as Crimson Perpetual before being uploaded by an anonymous poster here. Quatre Saisons Lelieur is a synonym for La Moderne, which is quite similar to Autumn Damask, and unrelated to Rose du Roi, aside from both being Damask Perpetuals associated with the Comte de Lelieur. This same confusion seems to have crept into descriptions of the rose as early as 1837. My own "Rose du Roi of commerce" is now in bloom, and of six flowers I examined, two had five sepals, three had six, and one had seven! Buist's 'The Rose Manual' (1844) and Cranston's 'Cultural Directions for the Rose' (1877) said Rose du Roi was a very good producer of seed, and mine has very large, oblong, purple-tinged hips on it (1.25" long and 3/4" across), and they still have a couple of months to grow before they'll be ripe. By Damask standards, they're enormous. Like the 1873 description, it has no prickles under the petioles, which is unusual.
I believe the "of commerce" label probably dates from Philip Robinson's 2007 article in Rosa Mundi, where he said that the rose in commerce in America was obtained from Kordes circa 1954, and that he'd "grown this rose for a number of years and had no reason to suspect that it was not the true variety." Then he obtained a rose identified as Panachee de Lyon, which did not appear identical (aside from bloom color) to what he grew as Rose du Roi, and concluded that the Panachee was authentic and the Rose du Roi was not. The alleged Panachee eventually produced a red sport, which Vintage Gardens sold as "Rose du Roi, original." Like him, I've grown the rose of commerce for years, and had no reason to doubt that it was either Rose du Roi or Mogador. I've yet to see his Panachee or its redder sport, but until such a time as I do, I'm unready to discount the idea that the rose in commerce is, if not Rose du Roi or Mogador, perhaps Louis Philippe, a seedling of Rose du Roi. Six sepals is just too unusual, and some of Rose du Roi's seedlings inherited it, as some did its prolific seed production.