A detailed and intriguing article about the Louis Mask, and the controversy of who owns it - the St Louis Art Museum, or the Egyptian State: "According to records held by the antiquities department the funerary mask of Ka-Nefer-Nefer was discovered in 1952 by Egyptologist Zakariya Goneim while he was excavating the area of the unfinished Step Pyramid of the Third- Dynasty ruler Sekhemkhet on the Saqqara necropolis. Along with many other finds from the excavation the mask was placed in the so-called Sekhemkhet magazine, which was situated to the south of the pyramid of Unas. This and all the contents of the magazine were the property of the Egyptian Antiquities Authority, now SCA . . . . A trawl through the museum's documents, however, has produced no evidence that the splendid mask ever entered the Egyptian Museum. Moreover, it was found that several of the other objects discovered by Goneim that had been sent immediately to the museum were stored unregistered until 1972 . . . . Although the story of Ka-Nefer-Nefer's discovery is well known, its means of exit from Egypt remains a perplexing mystery."
See the above website for the full story.