1. The brass version is raw brass, and as such it can oxidize. Some parts may show some discoloration due to this. To remedy, simply use a 3M scotch pad, or a fine steel wool to smooth the button surface prior to assembly.
2. It is recommended that the edges of the 3 "legs" on each button are chamfered or rounded by sanding the sharp edges. This is not always required, but can help ensure the button actuate freely and do not ever bind.