assassin's creed 2 i can't find the last weapon

i cant find the last weapon in assassin's creed 2 :confused:

With Assassin's Creed 2, there is one weapon you can only get when you gather 50 feathers. Every other weapon is bought in the 360 version.

The exception of this is with the PS3 version, where 6 additional weapons can be unlocked by linking up with Assassin's Creed Bloodlines.