This is a nice set of Wigglers or centre finders.  Made in the USA by General it is a most useful bit of kit.  In the plastic wallet is a selection of devices to allow you to find the centre or edge of a piece of work.  A main body allows the fitting of three attachements:  An offset indicator holder which allows the fittng of a dial indicator.  A .250″ dia contact ball which allows you to find the edge of piece of work.  And a needle point shaft which allows you to find the centre of a piece of work.  The attachments are clamped into the body which is then held in a chuck, usually in a milling machine.

I will try to demonstrate how to use this kit on future projects.