Brass Buttons

The Brass Buttons can be acquired by fighting the minions of Minax and are essential for the Stranger to complete the game. It appears in Ultima II

Description
This important item identifies you as an aviator and allows you to make use one of the several modern transports that you can find in the early days of Sosaria; Bi-Plane. It is also required to accelerate the aeroplane to flying speed. Once replaced, however, this button would break once flight was achieved.

A fair warning; ALWAYS check your inventory after an encounter with Pirates, before saving your game. It is well known that they steal important items, before you know it.