Tateno Kazumi at Nara kokuritsu bunka zai kenkyuujo for his opinion. He first brought the relic to my attention last fall, but I was so busy looking into medieval population that I forgot what he said. I'll pass along Tateno-san's view as soon as I have it. I don't know how many of you do mokkan or are interested, but Tateno-san is a really handy fellow to know. Any way thanks for the hints.
Further observations are welcome.
I hope I have responded appropriately. My computer does not have Japanese-language software. If you don't mind, I'd also like to have any information you have on sources. The Lantern Night Excursion of Chung K'uei. Julian Press, 1961.