Some entrepreneurs on Maranga IV claimed to have Molor's mummified head on display for a fee of fifty darseks per person. Their claim was unlikely to be true. (TNG: "Firstborn")
Such a claim, though, indicates that customers could believe it to be true and may be a reference to Klingon mummification.
In DS9: "Looking for par'Mach in All the Wrong Places" taking place in 2373, Worf enthusiastically mentioned the events in Qam-Chee to have happened "a thousand years ago." This would appear to be somewhat of a contradiction as TNG: "Rightful Heir" and TNG: "Firstborn" both state, that Molor, Lukara and Kahless lived five hundred years earlier. Either Worf "rounded" the number of years in his enthusiasm, or Molor and Kahless were at least five hundred years old, which while the maximum life span for Klingons has never been clearly defined, seems to be without precedent. Another solution would be that Worf counted in Klingon years, as 2373 corresponds to the Year of Kahless999.