To gun enthusiasts, knife collectors, and lovers of weapons of any and all kinds:
here's your ticket to the gun show! Specifically a ticket to be redeemed at the Merchant's shop.
With this, you'll have access to a weapon's exclusive upgrade at any time, regardless of the weapon's level.
Not only that, but once unlocked, the upgrade itself is free of charge!

Note:
This item will be added to the Treasures menu and will be available across all of your saved data.