Best quality nylon-tipped tweezers for handling watch batteries, fine tips grip the battery so easily. Before we imported these we were using (for our own use) Swiss tweezers of the same design, which cost us £35.00. The two are just about identical!

Why not use use ordinary metal tweezers?
Two reasons. 

Firstly, if you use metal tweezers and accidentally touch both sides of the battery, you will "short" it.  It will still work, but only for a few weeks instead of a two or three  years.  Secondly, getting greasy finger marks on a battery shortens its life, it might only last a few months instead of two or three years. In both cases your customer will complain.