The lucky dragonkin coin is an item that can be obtained as a rare reward from the Motherlode Maw or the Dragonkin Laboratory. It can be activated with 99 Summoning to unlock the Diddykin pet, which destroys the coin in the process.
The chance of obtaining this item from the Motherlode Maw is 1 in 5000[1]and 1 in 15000 when turning Crystal motherlode shards in.[2]. 1 in 50000 chance on the dragonkin laboratory only while having Lucky charm (dragonkin laboratory) in your inventory.