How so? - you ask. - The works of historians nearly always featured all kinds of "Kiprianovsky set of 1408", "Code of Photios 1418" ??and so on. Moreover, the Trinity Chronicle, kotoroypolzovalsya Karamzin when writing his "History of the Russian State", was written in 1408, "Rogozhsky chronicler" - about 1412-th. Karamzin Novgorod chronicle - about 1425th. And you say that there is no chronicles earlier 1450 th! The fact is, my dear, that the dating of the chronicles and codes you listed - it's fruit ... wanted to say "fancy", but let it be "research" of a number of source studies of historians. With that, we note not accept other specialists. Physically, such documents do not exist. There is what is called lists. That is the best chronicle texts written on sheets of paper, for watermarks (filigree) dating back to the time not earlier than the second half of the XV century. Even such a little. Perimuschestvenno it comes to 70s or 80s. Or have all of century XVI.