Apple Watch in can password of random generation, you can check anytime soon in Glance.
Incidentally, when is too period when you set the duration of the password from Apple Watch it is removed.
Past use passwords can be managed in the iPhone.
However, we can see only if you have permissions on the Apple Watch if you want to check the iPhone.
IPhone permissions method in the Apple Watch, so you can view the permissions button with a touch stronger in the application that was started on the Watch (Force Touch), you can allow tap the button.
As attention, you can not check the password history in other ways is only the access allowed by Apple Watch.