Analysis of information sources in references of the Wikipedia article "Jani Beg" in English language version.
The tamga ( a sign of ownership or of belonging to a clan ) drawn on the flag can be seen on coins minted in Bulgar and Bilyar at the time of the early Golden Horde. (...) Besides the Catalan atlas of 1375 there is also a 50 x123 cm Catalan map preserved in Paris.
But then, in 1347, to the Italians' delight, their opponents began to die off at an alarming rate - Janibeg's army was overcome by the Plague. Janibeg had no choice but to call off his siege, but not until he performed one last act of warfare against Genoa. Using the catapults designed to throw boulders and fireballs over the walls of fortified cities like Kaffa, Janibeg launched the Plague infested corpses of his dead men into the city. The Italians quickly dumped these bodies back into the sea, but the damage was done. Due to the squalid conditions forced upon Kaffa by the siege, it was ripe for the quick desolation of the Plague.
Tamga in the form of a two-pointed prong was retained on the coins minted in Bolgar, Mokhsha and the Crimea up until the reign of Janibek, marking the disappearance of this image for the rest of the 14th century.
