Back in the 60s, I made copies on Kodachrome of some color illustrations in Drevnosti Russkogo Gosudarstvo (1854). One of these was of the battle banner of Kniaz Posharsky. I then sat down with my calligraphy pen and India ink and very painstakingly made a precise transcription of the inscription on said banner - which ran around its entire rim.
At the time, I was pretty well "honed" on reading material from such an early period. Nevertheless, with the large number of contractions and letter positions, I was able to descipher only about 10% of the writing. Supposing that the priests at the Russian church here could make short work of it, I showed it to them. The results were just about nil. It has remained a mystery ever since - a Russian Rosetta Stone.
I send this to you in order to share the mystery. Perhaps you could put it on your Web page and some distant expert could shed some light on the matter. It might be an interesting experiment, at the very least.